RE-ESTABLISHMENT OF SUSPENDED RRC CONNECTION AT A DIFFERENT eNB

ABSTRACT

In order to re-establish a suspended RRC connection, the mobile device ( 101 ) in one example sends a connection re-establishment request message to the RAN ( 102 ) to have the suspended RRC connection re-established. The RAN node may need to attempt to retrieve the RRC connection data (either from memory or if from another network element if stored elsewhere/if the RRC connection was suspended by another RAN node) and verifies whether the RRC connection is valid. When verified, the mobile device ( 101 ) receives, in response to the message, a connection re-establishment command message from the RAN ( 102 ). In response to the message, the mobile device ( 101 ) re-establishes the RRC connection with the RAN ( 102 ), using the stored RRC connection information, and sends a connection re-establishment complete message to the RAN ( 102 ). The mobile device ( 101 ) and RAN ( 102 ) may then resume user plane data communication with each other.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system and inparticular the handling of connections between nodes in a wirelesscommunication system.

BACKGROUND

Wireless communications systems are known that enable wireless datatransfer between one or more user equipment (UE) and one or more BaseStations (BS) arranged to provide nodes of a cellular RAN. An increasein the prevalence of UEs operating on wireless cellular communicationssystems requires that such networks carry and support a wide variety ofdata traffic types and services. UEs can be viewed as generic computingplatforms with wireless connectivity, capable of running a wide-rangingvariety of applications and services that are either pre-installed bythe device manufacturer or are installed/downloaded by the useraccording to the user's specific usage requirements. The applicationsthemselves may originate from a correspondingly wide-ranging group ofsoftware houses, manufacturers and 3^(rd) party developers. Such UEplatforms may include mobile devices such as mobile telephones,‘smartphones’, personal digital assistants, handheld or laptopcomputers, tablet computers and similar mobile devices having wirelesscommunications connectivity, or similarly the UE referred to hereincould include fixed devices that are relatively immovable in normal use,such fixed devices having wireless connectivity to enable them tocommunicate using the wireless communications system. The UE platformsmay also include other device types comprising embedded communicationsconnectivity, such as household appliances, utility meters and securityand surveillance equipment, or consumer electronics devices such asstill or video cameras, audio/visual entertainment equipment and gamingplatforms.

Wireless communication networks often distinguish between user-planetraffic (which may be considered as carrying application-level userdata) and control-plane traffic (which may be considered as signallingused to enable or support transfer of the user plane data via thewireless communication network, including for example mobility controland Radio Resource Control (RRC) functionality). Examples of user planetraffic and services carried by wireless communication networks includevoice, video, internet/web browsing sessions, upload/download filetransfer, instant messaging, e-mail, navigation services, RSS feeds andstreaming media. Examples of control plane traffic include core-networkmobility and attachment control (so-called Non-Access Stratum (NAS)signalling), radio access network control (such as Radio ResourceControl (RRC)), and session control signalling.

Outside of (or “above”) the radio and core network communication layers,applications may utilise or combine a multitude of internet-based (orother proprietary) protocols to achieve a desired result whenprovisioning for a specific service. For example, a navigationapplication may utilise TCP for file transfer of mapping data from aserver to a device but may also employ protocols to support periodic oraperiodic keep-alive signalling towards the navigation server tomaintain the application-level connection in the presence ofintermediary network nodes such as stateful firewalls. Similarly, ane-mail application may employ particular synchronisation protocols toalign the mailbox contents on the UE with those in an e-mail server, butmay also employ periodic or aperiodic server polling mechanisms to checkfor new e-mail. The present disclosure concerns operating wirelesscommunication systems to provide UEs with connectivity to support suchapplications.

For a more complete understanding of this disclosure, reference is nowmade to the following detailed description that sets out certainembodiments, taken in connection with the drawings, which can be brieflydescribed as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system including an LTE RadioAccess Network coupled to an Evolved Packet Core Network, furthercoupled to an external packet data network such as the public internet.

FIG. 2 shows a block diagram of selected components of an example UE foruse in a wireless communication system in accordance with the presentdisclosure.

FIG. 3 shows an illustration of a control manager in a RAM of the UEshown in FIG. 2 for facilitating communications with a wirelesscommunication system in accordance with the present disclosure.

FIG. 4 illustrates the RRC connection states, DRX sub-states and thetransitions therebetween in LTE.

FIG. 5 is a message sequence chart illustrating a normal RRC connectionprocedure in a wireless communication system in which no RRC connectionsuspension functionality is provided.

FIG. 6 is a flow diagram illustrating a simplification of the RRCconnection process in a wireless communication system in which no RRCconnection suspension functionality is provided.

FIG. 7 is a flow diagram illustrating a simplification of the RRCconnection reactivation process in a wireless communication system inwhich RRC connection suspension functionality is provided in accordancewith the present disclosure.

FIG. 8 is a message sequence chart illustrating an exemplary RRCconnection suspension process in a wireless communication system inaccordance with the present disclosure.

FIG. 9 is an illustration of an exemplary mobility scenario for handlingby the mobility handling process signalling variants during RRCconnection suspension in accordance with the present disclosure.

FIG. 10 is a message sequence chart illustrating an example ofsignalling variant 1 in mobility processing alternative B in a wirelesscommunication system in which a UE has a suspended RRC connection.

FIG. 11 is a message sequence chart illustrating an example ofsignalling variant 2 in mobility processing alternative B in a wirelesscommunication system in which a UE has a suspended RRC connection.

FIG. 12 is a message sequence chart illustrating an example ofsignalling variant 3 in mobility processing alternative B in a wirelesscommunication system in which a UE has a suspended RRC connection.

FIG. 13 is an illustration of another exemplary similar to FIG. 9, inwhich the UE moves back into, and again out of, a cell of the RAN inwhich the suspended RRC connection is valid.

FIGS. 14, 15 and 16 are message sequence charts illustrating examplemethods for handling downlink (DL) data in the network in differentscenarios when the RRC Connection between a UE and a RAN is suspended.

FIGS. 17, 18 and 19 show message sequence charts illustrating exampleRRC reactivation methods for handling the resumption of user plane datatransfer for a UE having a suspended RRC Connection with a RAN.

FIG. 20 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 1.

FIG. 21 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 2.

FIG. 22 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 3.

FIG. 23 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 4.

FIG. 24 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 5.

FIG. 25 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 6.

FIG. 26 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 7.

FIG. 27 shows a message sequence chart illustrating an example of arepresentative scenario for mobility procedures.

FIG. 28 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 10.

FIG. 29 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 11.

FIG. 30 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 13.

FIG. 31 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 14.

FIG. 32 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 15.

FIG. 33 shows a message sequence chart illustrating the method ofhandling an RRC connection suspension in Example Scenario 16.

DETAILED DESCRIPTION

Many UE applications require or benefit from so-called always-onconnectivity, such that a seamless and continuous connection experienceis delivered to the user when using the UE and the applications runningthereon. Whist the appearance of seamlessness is presented to the userat the service level, this may in fact be accomplished without permanentor continuous connectivity at all protocol levels beneath theapplication layer. Instead, it may be the case that connections areestablished and released on a regular or as-needed basis in order todeliver the user data when required but to allow for certain powerefficiency or system efficiency savings in the UE during the interveningperiods of time. However, a frequent establishment and release of theseconnections may also entail significant use of system resources orresult in additional signalling loads within the network, and theassociated system resource and control overheads may become large. Forsome application traffic, this may counteract the power or systemefficiency benefits of employing such an “as-needed” connectionestablishment strategy. Systems and methods which are able to reducethese system resource and control overheads are therefore desirable suchthat overall system and power efficiencies are improved when attemptingto deliver a seamless user or service experience at the applicationlevel via the communications network.

The prevalence of a plethora of application types, services, and meansof service delivery in wireless communications systems results in acorresponding plethora of data traffic distributions and statistics thatare presented to the wireless communication networks for delivery.Wireless communication networks are therefore less able to predicttraffic profiles and distributions, and must be designed to adapt theconnections and the assigned transmission resources to the dynamicallyvarying (potentially “bursty”) traffic loads.

In order to do so, wireless radio access networks can include dynamicscheduling such that a quantity of assigned shared radio resources maybe varied in rapid response to data demand (e.g. data buffer status).Such dynamic scheduling typically operates on a time scale of one to afew milliseconds. At a time-scale above this (operating in the region of100 ms to a few seconds), wireless communication networks often alsoemploy a state-machine-oriented process to adapt a radio connectionstate or sub-state to the degree of observed traffic activity. Radioconnection states or sub-states may differ in numerous ways, including;the degree of connectivity offered, the quantity of system resourcesthat are reserved or used for the connection, and the amount of UEbattery power consumed.

The connectivity level can be characterised as a combination of variousconnectivity attributes such as:

-   -   Location granularity: The accuracy to which the wireless        communication network tracks the current location of the UE        (e.g. to the cell level for more active UEs, or to only a group        of cells for less active UEs)    -   Mobility control: The decision to change the cell to which the        UE is associated may be taken by the network (network controlled        mobility) or by the UE (UE controlled mobility). In the case of        network controlled mobility a UE may be instructed to perform        measurements and report measurement results to the network in        order to assist the network in making the decision to perform a        handover. Once a handover decision is made the network will        typically prepare any necessary resources in the target cell        before instructing the UE to change cell by sending a handover        command. In the case of UE controlled mobility, the UE will        perform measurements on neighbouring cells and use these        measurements in making a decision to perform a cell reselection.        The network can control the decision process by sending various        cell reselection parameters (e.g. threshold, offsets, etc) in        broadcast system information. Network controlled mobility        (handover) requires more over the air signalling, network        internal signalling, and network processing resource than UE        controlled mobility.    -   Assigned resources: The presence, absence, type or amount of        radio transmission resources available to the UE for performing        communication, as a function of expected activity level    -   Tx/Rx Readiness: The power consumed by UEs is often a function        of their “readiness” to transmit or receive. For example, a UE        must permanently activate its receiver in order to receive        downlink communication from a basestation if the data may arrive        at any given instant, resulting in high power consumption and        battery drain. To save power, discontinuous reception (DRX) is        often employed, allowing the UE to “sleep” and turn off its        receiver at certain times. The basestation (BS) must take the        UE's DRX pattern into account when determining the times at        which it will be able to successfully deliver data to the UE.        The activity cycle of a DRX pattern often varies as a function        of the assigned radio connection state or sub-state.    -   Interfaces or bearers established: End-to-end communications        (for example from a UE to a core network gateway or egress node        towards external networks such as the internet) may require that        user-specific connections (or bearers) are established between        all participating network nodes or entities. The establishment        of some of these interfaces may be associated with the radio        connection state or sub-state as a function of the current        activity level.

Disclosed herein are methods, apparatuses and software for use in awireless communications system to suspend and handle the reactivation ofa Radio Resource Control (RRC) connection for carrying user-plane andcontrol plane data between a UE and a RAN. Also disclosed herein aremethods, apparatuses and software for handling mobility control anddownlink data for a UE for which an RRC connection is suspended.

In the context of this disclosure the terms “suspending”, “suspend” or“suspension” in relation to an RRC connection mean storing a contextrelating to the RRC connection (or storing RRC connection data) and oneor more of:

-   -   inhibiting the transmission of user plane data between a mobile        device and a RAN node but the mobile device still able to        receive paging from the RAN node and/or to receive notifications        of downlink data from the RAN node;    -   a RAN node instructing a mobile device to perform functions (for        example, paging and mobility procedures that may differ from        those used in a normal or non-suspended RRC connected mode) that        are the same as or similar to idle mode functions; and    -   releasing the air interface or radio link(s) or radio resources        associated with the RRC connection between the RAN node and the        mobile device but the mobile device still being able to receive        paging from the RAN node and/or to receive notifications of        downlink data from the RAN node.

The RRC connection data or information (which can alternatively bereferred to as RRC context data) may include parameters or otherinformation related to an RRC connection or more general parametersrelated to the RRC layer or other layers. For example, it may includeparameters relating to the current configuration of radio bearers, radioresources, temporary cell identifiers, security parameters or keys, MACconfiguration, physical layer configuration and measurement andreporting configuration. It may also include data related to the RRClayer or other layers such as the physical layer, MAC layer, RLC layer,and PDCP layer. The security parameters or keys may, for example,include the K_(asme), K_(enb), K_(RRCenc), K_(RRCint), K_(RRCUPenc),integrity algorithm, encryption algorithm, and radio bearer COUNTvalues.

In accordance with a first aspect there is provided a method,implemented in a mobile device for use with a Radio Access Network(RAN), comprising:

-   -   the mobile device sending an indicator to the RAN in respect of        a radio resource control (RRC) connection with the RAN;        wherein the indicator indicates the preference of the mobile        device to have the RRC connection either suspended or released.        In accordance with a second aspect there is provided a mobile        device for use with a Radio Access Network (RAN), the mobile        device being configured to:    -   send an indicator to the RAN in respect of a radio resource        control (RRC) connection with the RAN;    -   wherein the indicator indicates the preference of the mobile        device to have the RRC connection either suspended or released.        Typically, the indicator is a preference to have the RRC        connection either suspended or released.        The indicator may be included in a request message sent by the        mobile device to a RAN node in the RAN. Alternatively, or in        addition, the indicator could be included in a capabilities        message sent by the mobile device to a RAN node in the RAN.

Preferably, the mobile device receives a command message from the RAN;and the mobile device in response to the command message does at leastone of:

-   -   releasing the RRC connection; and    -   suspending the RRC connection.        The command message may be received in response to the sending        of the indicator.        Preferably, the suspending of the RRC connection includes the        mobile device storing RRC connection data for the RRC        connection. The stored RRC connection data is usable by the        mobile device to re-establish the suspended RRC connection.        The stored RRC connection data may comprise data representing        one or more of:    -   the configuration of radio bearers in the RRC connection;    -   security parameters relating to the RRC connection and/or to the        RRC layer generally and not necessarily specific to the RRC        connection that is suspended;    -   temporary cell identifiers;    -   MAC configuration;    -   Physical Layer configuration; and    -   Measurement and reporting configuration.        In one example, the indicator may be sent in response to a RRC        connection suspension criterion being met at the mobile device.        Typically, the RRC connection suspension criterion comprises at        least one of:    -   the expiry of a timer at the mobile device;    -   no user plane data having been received from or sent to the RAN        for a time period;    -   no user plane data being expected to be received from or sent to        the RAN for a period of time;    -   a status of an input function or output function of the mobile        device;    -   a status of one or more applications of the mobile device; and    -   a higher layer indication to an RRC layer at the mobile device.        The higher layer indication may be from an application layer or        from a non-access stratum (NAS) layer.        Preferably, the mobile device initiates re-establishment of the        suspended RRC connection in response to:    -   the mobile device generating uplink data via the user plane of        an RRC connection; or reception at the mobile device of paging;        or    -   reception at the mobile device of a notification that the RAN or        a core network (CN) has downlink data buffered to send to the        mobile device.        The mobile device may be configured to communicate with the RAN        in accordance with an LTE or LTE Advanced protocol.        The RAN may be configured to communicate with the mobile device        in accordance with the LTE or LTE Advanced protocol.        The RAN node or nodes may be eNode B(s).        In accordance with a third aspect there is provided a method,        implemented in a node of a Radio Access Network (RAN) for use        with a mobile device, the method comprising:

receiving at the RAN node a request from the mobile device forre-establishment of a radio resource control (RRC) connection suspendedby another RAN node;

the RAN node attempting to retrieve RRC connection data relating to thesuspended RRC connection; and

the RAN node doing one of:

-   -   if the RRC connection is valid, sending a connection        re-establishment command message to the mobile device; and    -   if the RRC connection is invalid, sending a connection        re-establishment reject message to the mobile device.        In accordance with a fourth aspect there is provided a node of a        Radio Access Network (RAN) for use with a mobile device, the RAN        node being configured to:

receive a request for re-establishment of a radio resource control (RRC)connection suspended by another RAN node;

attempt to retrieve RRC connection data relating to the suspended RRCconnection;

if the RRC connection is valid, sending a connection re-establishmentcommand message to the mobile device; and

if the RRC connection is invalid, sending a connection re-establishmentreject message to the mobile device.

In some examples, the connection re-establishment command message may beone of a RRC Connection Reestablishment Command message or a RRCConnection Reconfiguration message. Other new or existing 3GPP messagesare also possible. Similarly, the connection re-establishment rejectmessage may be a RRC Connection Reestablishment Reject message. Othernew or existing 3GPP messages are also possible.Typically, the RAN node determines whether or not the suspended RRCconnection is valid by reference to the RRC connection data.The RAN node may determine whether or not the suspended RRC connectionis valid by at least one of:

-   -   determining that a timer has not expired; and    -   whether the RRC connection data is retrieved.        In one example, the RRC connection data is retrieved from        another network component. The other network component is a RAN        network component, such as a RAN node, or a core network (CN)        network component, such as a mobility management entity (MME).        However, other CN network components could possibly used, such        as a serving Gateway (S-GW).        In another example, the RRC connection data could have been        stored, by the other RAN node, in a memory device in the RAN        node and the RAN node retrieves it from the memory device.        The RAN node may retrieve the stored RRC connection data and        re-establish the suspended RRC connection in response to the        mobile device responding to a paging request or a notification        of downlink data.        The RAN node may retrieve the stored RRC connection data and        re-establish the suspended RRC connection in response to        receiving a re-establishment request message from the mobile        device for re-establishment of the suspended RRC connection.        The RAN node or nodes may be configured to communicate with the        mobile device in accordance with a LTE or LTE Advanced protocol.        The RAN node or nodes may be eNode B(s).        In accordance with a fifth aspect there is provided a method        implemented in a node of a Radio Access Network (RAN) for use        with a mobile device, the method comprising:

a RAN node transmitting radio resource control (RRC) connection data,relating to a RRC connection with a mobile device, to at least one othernetwork component; and

the RAN node suspending the RRC connection with the mobile device.

In accordance with a sixth aspect there is provided a node of a RadioAccess Network (RAN) for use with a mobile device, the RAN node beingconfigured to:

-   -   transmit radio resource control (RRC) connection data, relating        to a RRC connection with a mobile device, to at least one other        network component; and    -   suspend the RRC connection with the mobile device.        The at least one other network component may be a RAN network        component, such as a RAN node, or CN network component such as        MME. However, it is possible that the other network component        could be another CN network component, such as a S-GW.        The RRC connection data may also be stored at the RAN node.        Preferably, the RRC connection data transmitted to the other        network component is usable by the RAN node or another RAN node        to re-establish the suspended RRC connection.        The RRC connection data may comprise data representing one or        more of:    -   the configuration of radio bearers in the RRC connection;    -   security parameters, either relating to the RRC connection or        not specific to the RRC connection;    -   temporary cell identifiers;    -   MAC configuration;    -   Physical Layer configuration; and    -   Measurement and reporting configuration.        The RRC connection data may be marked to indicate the suspension        of the RRC connection.        Preferably, the RAN node transmits the RRC connection data to        the other network component and suspends the RRC connection, in        response to a suspension criterion being met.        The suspension criterion comprises at least one of:    -   the expiry of a timer at the RAN Node;    -   transmission of a message by the RAN node to the mobile device        to instruct release of the established RRC connection;    -   receiving at the RAN node a suspension request message from the        mobile device;    -   no user plane data having been received from or sent to the        mobile device for a time period;    -   no user plane data being expected to be received from or sent to        the mobile device for a period of time; and    -   a higher layer indication to a RRC layer        The higher layer indication may be from an application layer or        a non-access stratum (NAS) layer.        Typically, the RRC connection data comprises an identification        of the mobile device.        The RRC connection data may comprise an identification of a cell        serving the mobile device when the RRC connection is suspended.        Typically, the RAN node may send a message to inform any other        RAN node or a Core Network (CN) node that the RRC connection has        been suspended and the RRC connection data stored in the other        network component.        Preferably, the RRC connection data is transmitted to the other        network component for storage at the other network component.        The RAN may be configured to communicate with the mobile device        in accordance with a LTE or LTE Advanced protocol.        The RAN node or nodes may be eNode B(s).

In accordance with a seventh aspect there is provided a method in anetwork component, the method comprising:

-   -   receiving radio resource control (RRC) connection data from a        first radio access network (RAN) node, the RRC connection data        relating to a RRC connection between the first RAN node and a        mobile device, the RRC connection being suspended or to be        suspended by the first RAN node; and    -   storing the RRC connection data.

In accordance with an eighth aspect there is provided a networkcomponent configured to:

-   -   receive radio resource control (RRC) connection data from a        first radio access network (RAN) node, the RRC connection data        relating to a RRC connection between the first RAN node and a        mobile device, the RRC connection being suspended or to be        suspended by the first RAN node; and    -   store the RRC connection data.

Preferably, the network component may be a RAN network component or a CNnetwork component. For example, where the network component is a RANnetwork component, it may be a RAN node and where the network componentis a CN network component, it may be a MME. However it is possible thatthe CN network component may be a S-GW.

The first RAN node may be in a validity area of the MME where the othernetwork component is an MME.

Typically, the stored RRC connection data can be retrieved by a RAN nodeto re-establish the suspended RRC connection with the mobile device.

The RRC connection data can be retrieved by the first RAN node, thesecond RAN node or another RAN node (or third RAN node) to re-establishthe suspended RRC connection with the mobile device.

Preferably, the RRC connection data comprises data representing at leastone of:

-   -   the configuration of radio bearers in the RRC connection;    -   security parameters relating to either the RRC connection or        non-specific to the RRC connection;    -   temporary cell identifiers;    -   MAC configuration;    -   Physical Layer configuration; and    -   Measurement and reporting configuration.        Typically, the RRC connection data comprises an identification        of the mobile device.        The RRC connection data may comprise an identification of a cell        serving the mobile device when the RRC connection is suspended.        In accordance with a ninth aspect, there is provided a method,        implemented in a node of a Radio Access Network (RAN) for use        with a mobile device, the method comprising:

the RAN node sending a connection suspend command message to a mobiledevice to suspend a RRC connection with the mobile device.

In accordance with a tenth aspect, there is provided a Radio AccessNetwork (RAN) node for use with a mobile device, the RAN node beingconfigured to:

send a connection suspend command message to a UE to suspend a RRCconnection with the UE.

In one example, the connection suspend command message may be sent inresponse to a suspension criterion being met at the RAN node.The suspension criterion may be at least one or:

-   -   the expiry of a timer at the RAN Node;    -   receiving at the RAN node a suspension request message from the        mobile device;    -   no user plane data having been received from or sent to the        mobile device for a time period;    -   no user plane data being expected to be received from or sent to        the mobile device for a period of time; and    -   a higher layer indication to a RRC layer. The higher layer may        be an application layer or non-access stratum (NAS) layer.        The RAN node may receive from the mobile device, in response to        the connection suspend command message, an acknowledgement        message. The acknowledgement message may include an        acknowledgement from at least one of a RRC layer or a medium        access control (MAC) layer of the mobile device.        The RAN node may release mobility control of the mobile device        to the mobile device, while the RRC connection is suspended.        The RAN node may also store RRC connection data for the RRC        connection.        The RAN node may be an eNodeB.        According to an eleventh aspect, there is provided a method,        implemented in a mobile device for use with a Radio Access        Network (RAN), the method comprising:

the mobile device receiving a connection suspend command message fromthe RAN instructing the mobile device to suspend a RRC connection withthe RAN; and

the mobile device, in response to the connection suspend commandmessage, suspending the RRC connection.

According to a twelfth aspect, there is provided a mobile device for usewith a Radio Access Network (RAN), the mobile device being configuredto:

receive a connection suspend command message from the RAN instructingthe mobile device to suspend a RRC connection with the RAN; and

suspend the RRC connection in response to the connection suspend commandmessage.

The mobile device may send a connection suspend request message to theRAN requesting suspension of the RRC connection; and receive theconnection suspend command message from the RAN in response to theconnection suspend request message.The connection suspend request message may be sent in response to asuspension criterion being met at the mobile device.The suspension criterion may be at least one of:

-   -   the expiry of a timer at the mobile device;    -   no user plane data having been received from or sent to the RAN        for a time period;    -   no user plane data being expected to be received from or sent to        the RAN for a period of time;    -   a status of an input function of the mobile device;    -   a status of an output function of the mobile device;    -   a status of one or more applications of the mobile device; and    -   a higher layer indication to an RRC layer at the mobile device.        The higher layer may be an application layer or non-access        stratum (NAS) layer of the mobile device.        The mobile device may, in response to the connection suspend        command message, send to the RAN node an acknowledgement        message.        The acknowledgement message may include an acknowledgement from        at least one of a RRC layer or a medium access control (MAC)        layer of the mobile device.        The mobile device may control mobility while the RRC connection        is suspended.        The mobile device may be configured to communicate with the RAN        in accordance with a LTE or LTE Advanced protocol.        According to a thirteenth aspect, there is provided a method,        implemented in a node of a Radio Access Network (RAN) for use        with a mobile device, the method comprising:

the RAN node receiving from a mobile device a connectionre-establishment request message to have a suspended RRC connectionre-established;

in response to the connection re-establishment request message the RANnode sending a connection re-establishment command message to the mobiledevice; and

the RAN node receiving in response to the connection re-establishmentcommand message a connection re-establishment complete message from themobile device.

According to a fourteenth aspect, there is provided a Radio AccessNetwork (RAN) node for use with a mobile device, the RAN node beingconfigured to:

receive from a UE a connection re-establishment request message to havea suspended RRC connection re-established;

send a connection re-establishment command message to the UE, inresponse to the connection re-establishment request message; and

receive, in response to the connection re-establishment command message,a connection re-establishment complete message from the UE.

The connection re-establishment command message may be one of a RRCConnection Reestablishment command message and a RRC ConnectionReconfiguration message.The connection re-establishment complete message may be one of a RRCConnection Reestablishment Complete message and a RRC ConnectionReconfiguration Complete message.The RAN node may be an eNodeB.According to a fifteenth aspect, there is provided a method, implementedin a mobile device for use with a Radio Access Network (RAN), the methodcomprising:

the mobile device sending a connection re-establishment request messageto a RAN to have a suspended RRC connection re-established;

the mobile device receiving, in response to the connectionre-establishment request message, a connection re-establishment commandmessage from the RAN; and

the mobile device, in response to the connection re-establishmentcommand message, re-establishing the RRC connection with the RAN andsending a connection re-establishment complete message to the RAN.

According to a sixteenth aspect, there is provided a mobile device foruse with a Radio Access Network (RAN), the mobile device beingconfigured to:

send a connection re-establishment request message to a RAN to requestre-establishment of a suspended RRC connection;

receive, in response to the re-establishment request message, aconnection re-establishment command message from the RAN; and

re-establish the RRC connection with the RAN and send a re-establishmentcomplete message to the RAN, in response to the connectionre-establishment command message.

The connection re-establishment request message may be sent in responseto a re-establishment criterion being met at the mobile device.The re-establishment criterion may include at least one of:

-   -   the mobile device generating uplink data via the user plane of        an RRC connection;    -   reception at the mobile device of a page;    -   reception at the mobile device of a notification that the RAN or        a core network (CN) has downlink data buffered to send to the        mobile device; and    -   the mobile device reselecting to another cell.        The connection re-establishment command message may be one of a        RRC Connection Reestablishment command message and a RRC        Connection Reconfiguration message.        The connection re-establishment complete message may be one of a        RRC Connection Reestablishment Complete message and a RRC        Connection Reconfiguration Complete message.        The mobile device may be configured to communicate with the RAN        in accordance with an LTE or LTE Advanced protocol.        Preferably, one or more of the above aspects can be combined as        desired. In addition, features of any aspect may be combined        with another aspect where appropriate.

Long Term Evolution (LTE) is a Third Generation Partnership Project(3GPP) standard for wireless communication network technology. Anillustrative example of a wireless communication system 100 supportingcommunications in accordance with LTE is shown in FIG. 1.

The following detailed description is set out in the context of awireless communication system supporting LTE, but it should beunderstood that the applicability of the present disclosure is in no waylimited to LTE. Indeed the broad concepts of UE-RAN RRC connectionsuspension and handling thereof disclosed herein are equally applicablein other wireless communication systems supporting other technologiesand protocols, whether currently known or not yet envisaged. In thisrespect, the disclosure should in no way be limited to the followingillustrative implementations, drawings and techniques, but may bemodified and used in other wireless communication systems withoutdeparting from the scope of the appended claims, due regard being givento all equivalents.

LTE describes a plurality of requirements for wireless communicationssystems in evolved or advanced cellular broadband technologies. Suchrequirements include providing an Evolved Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access Network(E-UTRAN)—i.e. RAN 102. As shown in FIG. 1, RAN 102 provides ahigh-speed radio access technique to support wireless communicationsbetween UE 101 and one or more BS acting as nodes of the RAN 102 to meetthe increased network demands, including improving user throughputs andnetwork capacity, reducing latency, and increasing mobility. The LTE RAN102 shown in FIG. 1 comprises one node type acting as the node basestations (BS)—i.e. evolved Node Bs (eNB) 102 a,b, . . . n, advanced LTEequipment that supports an E-UTRAN air interface, and which can provideat least some of the functionalities of the BS, wireless access points,and other systems and devices some of which may be more evolved than theequivalent equipment in a traditional wireless telecommunicationssystem. The term eNB or access device may be used herein to refer to anydevice, existing or advanced, that may be used to gain access to anetwork. Such advanced or next generation equipment may be referred toherein as long-term evolution (LTE) equipment.

An eNB may support communications with UEs via one or more cells. Acommunication between an eNB and a UE may comprise communication via asingle cell of the eNB or may comprise simultaneous or non-simultaneouscommunication via more than one cell.

In some implementations, the functionality of an eNB may beself-contained within one physical node or entity, whilst in otherimplementations, said functionality may be distributed between more thanone physical node or entity with interconnections therebetween.

As can be seen in FIG. 1, the LTE wireless communication network 100provides a Uu radio interface between the UE 101 and the eNB 102 a ofthe RAN 102 to facilitate radio communications therebetween.

LTE uses an Evolved Packet Core (EPC) network architecture for the CoreNetwork (CN) 103 to support the RAN 102 (in the LTE case, the E-UTRAN).Thus, as shown in FIG. 1, the eNB RAN nodes 102 a,b . . . n formconnections with one or more nodes in the EPC CN 103 (described below).The EPC network architecture transports protocols such as TransmissionControl Protocol (TCP)/internet Protocol (IP) for supporting IP basedservices, such as voice, video, other media, and messaging, withend-to-end Quality of Service (QoS). The EPC network architecture alsoenables improved connections and hand-over to other fixed-line andwireless access technologies with improved mobility.

The LTE Radio Access Network 102 (E-UTRAN) coupled to an EPC CN 103 maybe further coupled to an external packet data network such as the publicinternet 104.

The EPC CN 103 shown in FIG. 1 comprises three node types—the ServingGateway (SGW) 103 a routes user-plane data within the core network, theMobility Management Endpoint (MME) 103 b handles mobility and connectioncontrol between the UE and the core network, and the Packet Gateway(PGW) 103 c ingress/egress node routes data between the core network andexternal networks. During a communications session between the UE 101,eNB 102 a and CN 103 an ‘S1’ network interface between the RAN 102 andCN 103 is formed, including a control plane bearer connection ‘S1-MME’(sometimes referred to as ‘S1c’) ‘S1-MME’ between the eNB 102 a and MME103 b, and a user plane bearer connection ‘S1u’ between the eNB 102 aand SGW 103 a. An ‘S5/S8’ interface between the SGW 103 a and PGW 103 cprovides user plane communications therebetween. MME 103 b may beconnected to SGW 103 a, for example via an ‘S11’ interface.

FIG. 2 shows a block diagram illustrating some example componentscomprised in an example UE 200 that can be used in the LTE-enabledwireless communications system as shown in FIG. 1. The UE 200 may be awireless device and its associated Universal Integrated Circuit Card(UICC) that includes a Subscriber Identity Module (SIM) application, aUniversal Subscriber Identity Module (USIM) application, or a RemovableUser Identity Module (R-UIM) application or the UE 200 might be thedevice itself without such a card.

UE 200 includes multiple components linked by a communications bus 201.A processor 202 controls the overall operation of the UE 200.Communication functions, including data and voice communications, areperformed through a communication subsystem 204. The communicationsubsystem 204 may take the form of modems, modem banks, Ethernetdevices, universal serial bus (USB) interface devices, serialinterfaces, token ring devices, fiber distributed data interface (FDDI)devices, wireless local area network (WLAN) devices, radio transceiverdevices such as code division multiple access (CDMA) devices, globalsystem for mobile communications (GSM) radio transceiver devices,worldwide interoperability for microwave access (WiMAX) devices, and/orother well-known devices for connecting to networks. The communicationsubsystem 204 may enable the processor 202 to communicate with theInternet or one or more telecommunications networks or other networksfrom which the processor 202 might receive information or to which theprocessor 202 might output information. In the context of FIG. 1, thecommunication subsystem 204 receives messages from and sends messages towireless network 206 which may be the RAN 102 shown in FIG. 1 for voicecommunications or data communications or both. A power source 208, suchas one or more rechargeable batteries or a port to an external powersupply, powers the UE 200.

The processor 202 interacts with other components of the electronicdevice including Random Access Memory (RAM) 210, mass storage 212(including but not limited to magnetic and optical disks, magnetic tape,solid state drives or RAID arrays), Read Only Memory (ROM) 214 anddisplay screen 216, which may be, for example, a Liquid Crystal Display(LCD). An i/o controller 218 sends and receives signals relative to oneor more user control devices, such as a touch sensitive overlay on thedisplay screen 216 to enable user interaction with the UE 200.

The processor 202 executes instructions, code, software or computerprograms it may access from communications subsystem 204, RAM 210, massstorage 212 or ROM 214. The processor 202 may comprise one or more dataprocessing units or CPU chips. The processor 202 may execute theinstructions solely by itself, or in concert with other locally orremotely provided data processing components or other components notshown in FIG. 2. In particular, the processor 202 is capable of carryingout instructions such that the UE 200 is operable to perform wirelesscommunications in an LTE network in accordance with the disclosure setout below.

For example, referring to FIG. 3, the processor 202 may carry outinstructions to instantiate and maintain a communications manager 301 inRAM 210 that in use operates the communications subsystem 204 to performsignalling to interact with RAN 102.

The communications manager 301 may instantiate, for example in the RAM110 of UE 201, an LTE protocol stack to provide, at the Access Stratumlayers of LTE, one or more of a Radio Resource Control (RRC) signallinglayer 302 that is typically responsible for the control of radio relatedfunctions, a Radio Link Control (RLC) signalling layer 303 that istypically responsible for the retransmission of lost data, a MediumAccess Control (MAC) signalling layer 304 that is typically responsiblefor controlling access to the Physical Layer (PHY) 305. Of course,layers of the protocol stack may be implemented elsewhere, for examplethe MAC and PHY signalling may be provided in the UE by firmware orhardware and so not maintained in RAM 110. Indeed, the implementation ofthe protocol stack in the UE shown in FIG. 3 is only one example of manypossibilities within the scope of the present disclosure, and isprovided for explanatory purposes only.

The LTE Physical Layer (PHY) uses advanced technologies, includingOrthogonal Frequency Division Multiple Access (OFDMA), multiple-inputand multiple-output (MIMO) data transmissions, and smart antennas tomeet the network demands above. The LTE PHY uses OFDMA for downlinktransmissions, for instance from a BS to a UE, which can communicate bytransmitting signals throughout a geographical region known as a cell.Additionally, Within one carrier, the LTE PHY uses Single CarrierFrequency Division Multiple Access (SC-FDMA) for uplink transmissions,for instance from the UE to the BS. The OFDMA and SC-FDMA technologiesfacilitate an increase in the system capacity and throughput whenperforming communications via an associated spectrum or bandwidth.

As mentioned above, the LTE system includes protocols such as a RadioResource Control (RRC) protocol, which is responsible for theassignment, configuration and release of connections and radio resourcesbetween the UE 101 and the eNBs 102 a,b, . . . n of RAN 102 or otheraccess or LTE equipment. The RRC protocol is described in detail in the3GPP TS 36.331 specifications. According to the RRC protocol, the twobasic RRC connection modes for the UE in LTE are defined as “idle mode”and “connected mode.”

During the connected mode or state, the UE 101 may exchange signals withthe network and perform other related operations, including the abilityto perform user-plane communications with the network, while during theidle mode or state, the UE 101 may shut down at least some of itsabilities and operations, and is no-longer able to perform user-planecommunications with the network. Idle and connected mode behaviours aredescribed in detail in the Third Generation Partnership Project (3GPP)specifications TS 36.304 and TS 36.331.

FIG. 4 illustrates the RRC state transitions for LTE. Transitionsbetween idle mode 401 and connected mode 402 in LTE are effected viaexplicit RRC connection establishment 403 (or setup) and release 404procedures and involve associated signalling overheads. During normalidle mode procedures, should a need for user plane communications arise,an RRC connection is established via the currently-camped cell. Thesequence of messages exchanged during a normal RRC connectionestablishment to transition between idle mode and connected mode in LTEis shown in FIG. 5. If the connection is UE-originated, an RRCconnection request message is sent (initiated using the PRACH randomaccess channel) by UE 101. Conversely, if the connection isnetwork-originated, the MME 103 a first requests for all eNBs 102 a,b .. . n within the known tracking area to send a paging message to the UE101 in order to stimulate the UEs sending of an RRC connection requestmessage.

Within the Connected Mode 402, UE 101 may implement DRX procedures,these being controlled within the Medium Access Control (MAC) layer. TheDRX pattern is defined via the use of multiple timers and processes thatmay be triggered by data activity or other events. However, the overalldegree of DRX may be conceptualised to exist in one of three predominantmodes, wherein one of these modes may be in use at any one time. It istherefore possible to consider these DRX modes as MAC sub-states of theRRC connected mode 402, each associated with a DRX level:

-   -   Continuous Reception 402 a: No DRX—the receiver of UE 101 is        always on and ready to receive user plane data over the RRC        connection.    -   Short DRX 402 b: The UE is allowed to turn off its receiver        (sleep, or DRX) for all but M out of N sub-frames (where a        sub-frame is a 1 ms unit of transmission time in the LTE        system), where M is a small value, such a 1 or 2, and N is a        relatively small value, such as 8.    -   Long DRX 402 c: The UE is allowed to turn off its receiver        (sleep, or DRX) for all but M out of N sub-frames, where M is a        small value, such a 1 or 2, and N is a relatively large value,        such as 256.

For correct system operation it is important that both the eNB 102 a andthe UE 101 are synchronised as to which sub-frames are categorised asDRX (the UE 101 may sleep) and which are not (the UE 101 may not sleep).To enable such co-ordination, inactivity timers may be configured (inboth the UE 101 and the eNB 102 a) in order to implicitly control (i.e.without signalling commands or orders) transitions towardsConnected-Mode DRX sub-states with increased DRX. In addition, MACcommands may also be used by the network (sent from eNB 102 a to the UE101) in order to explicitly direct a transition to an increased DRXsub-state.

When in the connected mode 402, any communication of new user plane datatypically results in a transition to the continuous reception sub-state402 a for a period of time determined by the ongoing packet dataactivity and an inactivity timer known as the DRX-InactivityTimer. Eachnew data packet resets the DRX-InactivityTimer to a preconfigured valueand when the timer expires, a transition from continuous reception 402 ato one of the DRX sub-states 402 b, 402 c is made.

In the LTE system, the mechanisms used to control UE mobility betweencells of the network differs between the idle 401 and connected 402modes:

-   -   In idle mode 401, mobility is UE-controlled (i.e. the UE 101        performs cell selection and reselection procedures as per 3GPP        Technical Specification 36.304 and in accordance with related        configuration parameters set by the network). Following        selection or reselection of a new cell by the UE 101, the UE 101        will inform the network of its new location only if the new cell        belongs to a tracking area that is different from the tracking        area of the previous camped cell. A tracking area is a group of        cells—which cells belong to which tracking area is dependent        upon network configuration. Thus, in idle mode 401, mobility        reports are only seldom sent by the UE 101, and the network is        aware of the UE's location with relatively coarse granularity        (tracking area level as opposed to cell level).    -   In connected mode 402, the UE 101 performs measurements of other        cells (on the same or other frequencies) according to the        configuration sent to the UE 101 by the network in measurement        control messages. The measurements are reported by the UE 101 to        the network wherein they are used by the network to make        handover decisions. Subsequent to a handover decision by the        network, the UE 101 is instructed to move to another cell or        frequency. Thus, in connected mode 402, measurement reports may        be sent relatively frequently and the network is aware of the        UE's location with finer granularity (to the cell level).

The RRC and MAC/DRX sub-states for LTE are summarised in Table 1 below.

TABLE 1 Radio Access Core Network LTE Bearers Bearers Radio RRC/MACEstablished (Uu, Established Resources Location Mobility State/substateS1) (S5/S8) Available Accuracy Control DRX Connected, Yes Yes Yes CellNetwork No Cont. Rx Connected, Yes Yes Yes Cell Network Short sleepShort DRX (return to continuous) Connected, Yes Yes Yes Cell NetworkLong sleep Long DRX (return to continuous) Idle No Yes No Tracking UELong sleep Area

As will be evident from the description below, the present disclosuresets out a method, usable in, for example, an LTE wireless communicationnetwork, of suspending an RRC connection such that at least user planecommunications between the UE and eNB are disabled (i.e. not able to betransmitted or received by the UE and the eNB), but in which thesuspended RRC connection can be efficiently reactivated such thatcommunications between the UE and eNB are resumed across the same‘established’ RRC connection, without a new RRC connection having to becreated. This provides significant advantages for wirelesscommunications systems for the following reasons.

Some applications running on UEs may generate traffic that requires theprovision of transmission resources only infrequently or for shortperiods of time. Traffic of this nature may be characterised as ‘bursty’or ‘sporadic’ and may involve extended periods of time with little or nodata activity. When handling such traffic within the system, frequentRRC state transitions from idle mode 401 to connected mode 402 for theUE 101 would each involve significant signalling exchanges between theUE 101 and the RAN 102, and/or between the RAN 102 and the CN 103. Thesignalling may for example be needed to:

-   -   1. establish or reconfigure Radio Bearers (e.g. over the Uu        interface between the UE 101 and the RAN 102),    -   2. establish or reconfigure other bearers, bearer segments, or        communication paths (e.g. the S1 bearer(s) between an LTE eNB        102 a,b . . . n and the SGW 103 a, or the S5/8 bearer(s) between        the SGW 103 a and PGW 103 c),    -   3. carry out security procedures to establish secure        communications,    -   4. establish or reconfigure physical radio resources to be used        for or during the connection and/or,    -   5. configure other parameters related to operation within the        RRC connected mode.

If, for reasons of network efficiency, the UE 101 were kept always inRRC connected mode 402 while handling such traffic, such that repeatedstate transitions and the related network messaging overhead describedabove were avoided, this could lead to high power usage and shorterbattery life for the UE 101 due to the relatively high powerrequirements of being always on in RRC connected mode 402. This ispartly because in RRC connected mode 402 mobility is always networkcontrolled at the cell level (which involves measurement reporting fromthe UE). In addition, although DRX cycles (controlled by the MAC layer)may be employed to reduce UE power consumption during times of datainactivity, mobility still remains network controlled and also, theconnected-mode DRX configuration is set by the network and may notprovide the UE with power consumption comparable to that of idle mode401. Furthermore, some radio transmission resources may be assigned,reserved or used by the UE for control signalling purposes when inconnected mode even though there may be no immediate user-plane data fortransmission. The connected mode DRX sub-state may thus exhibitexcessive power consumption for the UE 101 or inefficient use of systemresources for the RAN 102, whilst a transition to idle mode 401 (andsubsequently back to connected mode 402 on resumption of data activity)may incur significant signalling overheads to execute.

As will be evident from the following description, suspending the RRCconnection, as set out in the present disclosure, provides advantagesover these two techniques of controlling wireless communication systemsparticularly during so-called ‘bursty’ or sporadic data transfer to UEs(i.e. repeated state transitions or of holding the UE in a DRX sub-stateof connected mode 402), such that, in the present disclosure, networktraffic and power consumption can be relatively low, and battery lifecan be relatively high.

In the present disclosure, rather than a UE 101 that is in a connectedmode 402 but which is temporarily inactive (i.e. due to no immediatedata transfer being needed during an inactive time period of bursty orsporadic communications) transitioning to an idle mode 401 or to aconnected mode DRX sub-state 402 a, 402 b, the UE 101 instead isconfigured to perform UE controlled mobility (UE autonomous cellselection/reselection) and DRX procedures as if it were in idle mode(the idle mode configuration is reused thereby obviating the need for anew RRC state definition or configuration). However, whilst behaving asif in idle mode, the RRC connection for the UE may be considered to be“suspended” (as opposed to released). The difference between an RRCsuspension and an RRC release is that some or all of the RRC connectioninformation or RRC context is not discarded but is instead stored at anetwork component in either the radio access network (RAN) or the corenetwork (CN), such as at one or more eNBs 102 and/or mobility managemententity (MME) 103 b and/or stored at the UE 101.

The stored (suspended) RRC connection information may comprise, forexample, one or more of: parameters relating to the currentconfiguration of radio bearers, radio resources, temporary cellidentifiers, security parameters or keys, MAC configuration, physicallayer configuration and measurement and reporting configuration. The RRCconnection information or RRC context information) may also consist ofdata related to the RRC layer or other layers such as the physicallayer, MAC layer, RLC layer, and PDCP layer. The security parameters orkeys may, for example, include the K_(asme), Kenb, KRRCenc, KRRCint,KRRCUPenc, integrity algorithm, encryption algorithm, and radio bearerCOUNT values. Thus one or more components of a radio connection“context” still exist in memory within a network component and UE 101,but these may be labelled as ‘inactive’, ‘dormant’ or ‘suspended’. Thismay mean that one or more of the stored RRC connection parameters maynot be used for immediate user plane communications between the UE 101and the eNB 102 a without first executing one or more of: a step ofdetermining their current validity, a step of reactivating orre-establishing the connection via a cell of the radio access network inorder to return to the normal connected mode from the suspended state.

When a RRC connection is suspended, components of the RRC context datamay be stored or maintained in the UE and/or network. The criteria fortriggering or initiating a connection suspension, may be linked to theactivity or profile of the data resulting from one or more applicationsrunning, open or in use on the device. This may include estimations,predictions or measurements of the data volume or data rates required bythe radio connection or by one or more applications, It may furthercomprise estimations, predictions or measurements of packet arrival orinter-arrival times.

The criteria for triggering may also be linked to a status of the UE orof a mobile device connecting to the RAN via the UE. Aspects of the UEstatus may include one or more of:

-   -   A degree of user interaction with the device, for example        whether a keyboard of the device has been recently touched, the        status of a screen or screen backlight, whether a touchscreen        has been recently touched, the status of other user input        devices or devices responding to user input gestures    -   The execution status of running applications, including whether        or not the applications are open, running in the foreground or        background, stored in a suspended or hibernated state in memory    -   The protocol status of running applications, including whether        or not acknowledgements or replies from a peer entity are        pending and whether further data exchange is expected for        example within a time period

In yet further alternatives, the criteria for triggering may be linkedto an application activity, application type, application label, orapplication identifier, The criteria for triggering may further belinked to an application status or characterisation, such as whether ornot the application is running in a background mode of communication. Abackground mode of communication may comprise a state wherein thecurrent Quality of Service (QoS) requirements may be relaxed from anormal QoS level for example due to an absence of recent userinteraction with the device, or due to a latency tolerance of theapplication data.

The criteria for triggering may also be linked to a mobility conditionof the UE, for example, to a speed of motion or to a recent, current orexpected number of cell changes per unit of time. At higher speeds itmay be desirable to trigger (or to more readily trigger) a transition tothe RRC suspended state in order to avoid the need fornetwork-controlled handover procedures and the signalling overheadsassociated therewith, Received or reported radio conditions such assignal to noise or signal to interference ratios, signal power orquality estimates, or the pathloss between a node within the RAN and theUE may also form part of the criteria used to initiate a suspension ofan RRC connection.

The decision to initiate the suspension of the connection can be madeeither at a higher layer such as an application manager, operatingsystem controller or manager function, the NAS (non-access stratum)level or at an AS (access stratum) level such as the RRC, MAC orphysical layer level with inputs from user plane entities, or fromdevice input/output functions, from radio receiver or signal processingfunctions or from applications.

The eNB is typically in control of connection suspension although thesuspension may be initiated by either the UE or the eNB. In the UEinitiated case, the eNB may take a decision to suspend a connectionfollowing a request for suspension received from the UE. However, theeNB could also decide not to suspend the RRC connection following arequest for suspension from the UE or decided to release the RRCconnection. This could occur, for example, because the eNB is aware ofsomething that the UE is not aware of, such as downlink user plane datafor the UE. In the eNB initiated case, the eNB may decide to suspend theUE's connection without receiving a suspension request from the UE.

RRC connection suspension can happen in one of two ways,

-   -   a. Implicitly by associating a suspension with another event or        trigger, this usually (but not necessarily) being commonly known        to both the UE and the eNB. The suspension may occur at the same        time as the other event, or may occur at a time linked to the        other event, for example by means of a timer or timer expiry.        The implicit suspension may occur in either the UE and/or the        eNB or    -   b. By using explicit signalling exchanged between the UE and the        eNB (or vice versa)

In some embodiments, should a need for user plane communications arisefor a UE with a suspended RRC context, the RRC connection may only beused (by the network or UE as appropriate) following a precursory checkas to whether the suspended RRC connection or associated suspended RRCcontext is currently valid. A valid suspended RRC context is one whichmay potentially be freed from suspension (i.e. ‘reactivated’ orre-established) without the need to release the RRC connection andestablish a new one. Thus, if the RRC context is deemed ‘valid’, the UE101 or eNB 102 a may initiate reactivation or re-establishmentprocedures instead of procedures that establish a new RRC connection(and which would not utilise the stored RRC context data). A valid RRCcontext that has been freed from suspension is again ready for use suchthat user plane communications between the UE 101 and eNB 102 a may beresumed without the need for extensive RRC release, establishment orsetup procedures. The set of cells on which the RRC context is deemed‘valid’ is termed a validity area. Within the validity area, the UE ornetwork may initiate or attempt reactivation or re-establishmentprocedures for a previously-suspended RRC connection.

The set of cells in which the UE deems the RRC context is valid may bethe same as or different from the set of cells in which the networkdeems the RRC context to be valid. Thus the UE's validity area may bethe same as or different from the networks validity area. If either theUE or the eNB attempts to reactivate or re-establish the suspended RRCcontext in a cell where the peer entity (eNB or UE) does not deem theRRC context to be valid, then the reactivation or re-establishment maynot be successful and the a new RRC connection may be established.

An “RRC-reactivation” or “re-establishment” message or procedure isrequired to reactivate a previously-suspended RRC connection and toallow user plane data to be transferred (using part or all of thepreviously-stored RRC connection configuration). This procedure may becarried out either within the cell in which the RRC connection waspreviously suspended (the ‘suspension cell’), or within a new cell.Similarly, the procedure may be carried out in communication with an eNBto which the UE was connected when the RRC connection was previouslysuspended (the ‘suspension eNB’), or in communication with a new eNB.

In some cases, a suspended RRC connection may be reactivated (orre-established) without modification to the RRC context, itsconfiguration or its parameters. In this case, the RRC connection may bereused in order to continue to handle the user plane communications.This scenario may be more likely if the reactivation or re-establishmentprocedure is carried out within the suspension cell, or within a cellcontrolled by the suspension eNB. This is particularly useful whenhandling bursty-type data traffic, and can conserve power and keepcontrol plane traffic associated with RRC connection handling low. Inother cases, one or more components of the stored RRC context may needto be updated during the reactivation or re-establishment procedure.This scenario may be more likely if the reactivation or re-establishmentprocedure is carried out within a cell other than the suspension cell,or within a cell that is not controlled by the suspension eNB.

In yet further cases, it may not be possible or allowed to reactivate orre-establish a suspended RRC context. The criteria that govern whether asuspended RRC context may be reactivated or re-established may bepre-established within a standard or may be provided via a configurationstep to the UE, an eNB or to another network entity. A decision may alsobe taken not to reactivate or re-establish a suspended RRC context if itis determined that many components of the stored RRC connection wouldrequire updating. In this case, normal RRC connection establishmentprocedures may be followed as in the case of a normal idle mode UE (i.e.RRC connection setup following either a random access or pagingprocedure).

A simplified view of this RRC reactivation process is shown in the flowchart of FIG. 7.

This may be contrasted to the normal RRC connection setup proceduresfrom idle mode shown in FIG. 6, where no RRC suspension functionality isprovided in the wireless communication network. By comparing the flowchart of FIG. 7 with FIG. 6 it can be seen that, in accordance with thepresent disclosure, subsequent to the suspension of an RRC connection,when a need for user plane data communication arises and it isdetermined that a suspended RRC connection or associated suspended RRCcontext is ‘valid’, the RRC connection can be successfully reactivatedby an RRC connection reactivation or re-establishment process before theuser plane data may be transferred. Optionally, various RRCconnection/context validity criteria may first be checked in the UE 101or the eNB 102 a or in both before the RRC connection reactivation orre-establishment process is triggered. Also due to the fact that a validS1 interface must also exist prior to communication of user plane data,nodes of the CN 103 (such as the MME 103 b) may also be involved inchecking the validity status of the suspended RRC connection whenreactivation is required. Examples of validity criteria that may beemployed as inputs to the decision process are listed below:

-   -   Whether the UE 101 is currently camped on the same cell as the        cell to which it was connected when the RRC context was        suspended. Typically, an RRC configuration applies on a per cell        basis and it may be the network policy that the context only        remains valid if the cell hasn't changed. Note that this does        not exclude the possibility for the UE 101 to have moved out of        the cell in which the RRC context was suspended, and back in        again to the same cell. In these cases the RRC context may still        be reactivated and is considered a valid suspended RRC context.    -   Whether the UE 101 is currently camped on the same group of        cells as the group of cells to which it was connected when the        RRC context was suspended. An eNB 102 a, b, . . . , n would        typically support multiple cells, allowing for significant        co-ordination between those cells at the radio resource        management and RRC level without the need for standardised        interfaces. Thus a UE's RRC context information may be visible        to a group of cells (such as in the same eNB 102 a,b . . . n)        and an operator or network vendor may choose to coordinate some        aspects of the RRC configuration between them. This could enable        an RRC connection that was suspended within one cell under an        eNB 102 a to be reactivated or re-established under another cell        of the same eNB 102 a. In scenarios such as this, knowledge of        whether a UE 101 is still attached to the same eNB 102 a,b . . .        n (or other defined group of cells) may be useful when checking        whether such a reactivation is possible or allowable. The group        of cells may alternatively comprise a tracking area. In a        further alternative, each of the group of cells in which the RRC        context is deemed valid may not be controlled by the same eNB        102 a,b . . . n. In this case, there may be a need for the RRC        context information to be transferred from an ‘old eNB’ (the eNB        responsible for the previous suspension) to a ‘new eNB’ (the eNB        controlling the cell in which the UE is located at the time of        the attempted reactivation or re-establishment). This transfer        of RRC context information would be needed in order to complete        the reactivation or re-establishment process with the new eNB.    -   Whether an elapsed period of time since the RRC connection was        suspended is lower than a predetermined timer expiry threshold.        The system may wish to restrict the length of time for which an        RRC connection may be retained in the suspended state. Suspended        connections with an age beyond a preconfigured value are no        longer considered valid.

As described above, in accordance with the present disclosure a UE 101in a temporarily-inactive connected mode (i.e. having a ‘suspended’ RRCconnection) performs UE-controlled mobility (UE autonomous cellselection/reselection) and DRX procedures as if it were in idle mode,and during this time the RRC connection for this UE may be considered tobe “suspended” (as opposed to released). However, the condition or stateof the UE during this time may of course be viewed in different ways,for example:

-   -   1. The UE 101 may be viewed as being in idle mode (as it        performs UE-controlled mobility and idle mode DRX procedures)        but with some or all of the configuration associated with its        most recent RRC connection remaining stored to allow quick and        efficient reactivation or re-establishment of the old RRC        connection under certain circumstances.    -   2. The UE 101 may be viewed as remaining in the RRC connected        mode but being configured to perform UE-controlled mobility and        DRX procedures similar to idle mode. All or most of the RRC        connection information remains stored in the UE 101 while some        parts of the RRC configuration may be released.    -   3. The UE 101 may be viewed as remaining in the RRC connected        mode but being placed in a new state or sub state or mode in        which it performs UE-controlled mobility and DRX procedures        similar to idle mode. All or most of the RRC connection        information remains stored in the UE 101 while some parts of the        RRC configuration may be released.

Indeed, it is not intended that the present disclosure is limited to theUE being considered in the connected mode but with the RRC connection‘suspended’. Rather the present disclosure sets out a methodology ofhandling RRC connections between a UE and a RAN, and the UE-relatedconnections between the RAN and the CN such that transfer of user planedata between the UE and RAN is disabled and the data representing theRRC connection is stored such that user plane data transfer can later beresumed (on the same cell/eNB or on a different cell/eNB) using the same‘established’ RRC connection without that RRC connection being‘released’ (i.e. abandoned) and without a new RRC connection needing tobe created. This methodology can be utilised not just in wirelesscommunication systems supporting LTE, but also in other wirelesscommunications protocols.

The methods associated with implementing and supporting the RRCConnection suspension and reactivation procedures of the presentdisclosure will now be described in more detail, including somealternatives and variants that are possible. The procedures associatedwith RRC Connection suspension and reactivation can be divided into fouraspects which are described in the following sections:

-   -   RRC Connection Process    -   Processes handling mobility (i.e. procedures as the UE moves)        during RRC Connection Suspension    -   Processes handling receipt of downlink (DL) data during RRC        connection suspension    -   Processes handling a suspended RRC Connection to resume Uu data        transfer

The methods and other modes of operation described herein of the UE 101,eNB 102 a,b . . . n, SGW 103 a, MME 103 b and other CN nodes within thescope of the present disclosure may be provided at least in part by oneor more processors within the UE 101, eNB 102 a,b . . . n, SGW 103 a,MME 103 b and other CN nodes executing machine readable instructions toconfigure them to function accordingly to carry out said methods. Theinstructions may be provided as computer software products. Eachcomputer software product may be provided in, on or supported by acomputer readable medium which could be provided as all possiblepermanent and non-permanent forms of computer readable medium eithertransitory in nature, such as in a data transmission signal for examplesent over the internet, or non-transitory in nature such as in a RAM orother, non-volatile storage. On the other hand the computer readablemedium may be a non-transitory computer readable medium comprising allcomputer-readable media, with the sole exception being a transitory,propagating signal.

RRC Connection Suspension Process

In the UE 101, when the RRC Connection suspension occurs the UE 101 maybe configured to perform idle mode mobility and paging receptionprocedures while keeping stored for possible re-use some or all of itsRRC context information. The stored RRC context information may includethe following:

-   -   The configuration of Established Data Radio Bearers (DRBs) and        Signalling Radio Bearers (SRBs) including, for each radio        bearer, the PDCP configuration and current state (e.g. counter        values, etc) and the RLC configuration and status (e.g. counter        values, etc).    -   Security configuration and state (e.g. cipher and integrity        algorithm, counter values, etc)    -   Measurement reporting configuration.    -   Last used cell identity and cell specific user identity        (C-RNTI—“Cell Radio Network Temporary Identifier”)

In addition, the stored RRC context may also include other informationsuch as (but not limited to) configuration information or parametersrelating to any allocation of radio resources, MAC configuration,physical channel configuration or physical layer configuration data.

In the network, when the RRC Connection Suspension occurs, one or moreeNB's such as eNB's 102 a and 102 b and/or an MME 103 b store forpossible re-use some or all of the UE's RRC context information. The RRCcontext information stored in the network should correspond to thatstored in the UE 101. In addition, there are two main alternatives tothe network side suspension procedure depending on whether the eNBinforms the CN about the suspension at the time it occurs:

RRC Connection Suspension Alternative A-CN not Informed of Suspension

-   -   If the CN 103 is not informed of the suspension (by either the        UE 101 or the eNB 102 a), the S1 user plane between the S-GW 103        a and the eNB 102 a will remain active and any inbound        network-originated data will be forwarded by the S-GW 103 a over        the S1 to the corresponding eNB 102 a where it would need to be        buffered pending delivery to the UE 101. It is then the        responsibility of the eNB 102 a to contact and deliver the data        to the suspended UE 101. If the suspended UE RRC context is        found to be invalid at this time (e.g. because the UE has moved        or reselected to another cell without informing the network),        the eNB 102 a would need to initiate additional procedures        (involving other eNBs such as eNB 102 b and/or the CN 103) to        locate the UE 101 and to route the data to the correct eNB 102 b        . . . n and onward to the UE 101 (procedures for contacting the        UE 101 in this situation are discussed below). Alternatively,        rather than routing data on towards the correct eNB 102 b . . .        n once the UE 101 is located, the data may be discarded and        higher layer protocols (for example, TCP/IP) may instead be        relied upon to ensure eventual delivery.

RRC Connection Suspension Alternative B-CN Informed of Suspension

-   -   If the CN 103 is informed of the suspension (e.g. by either the        UE 101 or the eNB 102 a), it may optionally take action to also        suspend the S1 user plane between the S-GW 103 a and the eNB 102        a. The S1 user plane suspension may only affect the way that the        S-GW 103 a treats DL user data arriving in the S-GW 103 a.        Hence, in this case it may be considered as just a DL 51 user        plane suspension such that any inbound network-originated data        is buffered at the S-GW 103 a pending delivery to the UE 101. It        is then the responsibility of the CN 103 (i.e. MME 103 b and/or        S-GW 103 a) to identify the location of the UE and to        subsequently contact and deliver the data to the suspended UE        101. It is also possible that the CN 103 does not suspend the S1        user plane for a UE 101 upon having been informed of a        suspension of the UE's RRC Connection.

The CN 103 would typically be notified of a suspension through receiptof a notification message from the eNB 102 a. It is also possible thatthe UE 101 could inform the CN 103 of a connection suspension (e.g.following its receipt of a suspend message from the eNB 102 a), althoughthis may be less preferable due to the fact that this would involveadditional signalling over the air interface.

A CN node (e.g. MME 103 b and/or S-GW 103 a) may maintain a validityindicator for each UE (effectively this may relate either to whether anactive S1 user plane exists for the UE, or to the current validitystatus of a suspended S1 user plane for the UE). This indicator may beset based upon one or more separate sub-criteria such as location-basedcriteria or timer-based criteria. The location-based validity criteriamay involve for example recording a cell or eNB 102 a,b . . . n fromwhich the RRC suspend notification was initially received and settingthe location validity indicator to TRUE if the currently-known locationof the UE 101 matches the validity criteria, and setting the locationvalidity indicator to FALSE otherwise. The timer-based validity criteriamay involve setting a timer-based validity indicator to TRUE if anelapsed time since the RRC connection suspension (or S1 connectionsuspension) is lower than a threshold value and to FALSE otherwise. Bymeans of example, the overall validity criteria may comprise setting anoverall validity indicator to TRUE if both the location validityindicator and the timer-based validity indicator are TRUE, and settingthe overall validity indicator to FALSE otherwise.

An example message sequence chart of events related to an RRC Connectionsuspension is shown in FIG. 8. Steps E-G of the process described below(but not all shown in FIG. 8) are only carried out if the CN 103 isinformed of the suspension (otherwise these steps are omitted). Thesteps of the RRC connection suspension process shown in FIG. 8 can bedescribed as follows:

-   -   A. A UE 101 is in connected mode.    -   B. Criteria triggering a suspension of the UE's RRC Connection        are determined to have been met. The determination may be made        either by the UE 101 or by the eNB 102 a, or by both the UE and        the eNB. If the determination is made by the UE 101, the UE may        send an RRC connection suspend request message to eNB 102 a.    -   C. The UE's RRC Connection is suspended. This may be achieved        via implicit mechanisms such as the expiry of an inactivity        timer in both the eNB 102 a and the UE 101, or via explicit        mechanisms such as the sending of a message or command from the        eNB 102 a to the UE 101 to instruct the suspension of the RRC        Connection. In the implicit case, the eNB 102 a and UE 101 enter        the suspend state at approximately the same time but no suspend        message need be sent.    -   D. The UE 101 and eNB 102 a suspend the RRC connection. The Uu        connection is effectively ‘deactivated’ such that no user plane        data is transferred between the eNB 102 a and UE 101 but RRC        connection information is stored by both the UE 101 and the eNB        102 a. In some cases (not shown), the RRC connection information        may also be forwarded by eNB 102 a to another eNB within RAN        102, or to a node within the core network 103, such as MME 103        b. The UE 101, however, continues to monitor for paging or        notification of downlink data (see below).    -   E. The eNB 102 a may optionally send an S1 user-plane suspend        message to the MME 103 b and/or SGW 103 a (possibly via the MME)        to inform the CN 103 of the RRC suspension. The message may        include fields to identify the one or more UEs and possibly        bearer identifiers that have been suspended.    -   F. The MME 103 b may deactivate (but store in memory) the        existing S1-MME (S1c) bearer context associated with the UE 101.        ‘Deactivating’ is understood here to mean that data ceases to be        transferred over the bearer.    -   G. The SGW 103 a deactivates (but stores in memory) existing        S1-u user plane bearer contexts associated with the UE. Again,        ‘deactivating’ is understood here to mean that data ceases to be        transferred over the bearer.

Specific actions taken by the CN 103 in response to receipt of an S1suspend may therefore include:

-   -   Deactivating (but storing, pending reactivation) one or more S1        user plane and/or S1-MME bearer contexts in the SGW 103 a and        MME 103 b respectively, or in eNB 102 a    -   Buffering of any network-originated user data at the SGW 103 a        pending resumption of the S1 user plane    -   Monitoring for inbound tracking area or other location/cell        updates at the MME 103 b from the UE who's RRC connection has        been suspended (in order to assist with determining validity        status in the event of a need for reactivation)

In order for the RRC Connection suspend process above to be used, boththe UE 101 and the network of the wireless communication system need tobe configured to support this functionality. An RRC Connectionsuspension support indicator may be included in a UE capabilitiesmessage that is transferred from the UE 101 to the network.Alternatively, support for RRC connection suspension in the UE may beimplicitly inferred by the eNB as the result of the UE indicatingsupport for another (but associated) feature or UE capability within theUE capability message. As a further alternative the support for RRCconnection suspension in the UE may be implicitly inferred by the eNB asthe result of the reception of an RRC Connection Suspend Requestmessage. If the eNB determines that the UE supports the RRC Connectionsuspend functionality then the eNB 102 a can choose to configure the UE101 with appropriate parameters to trigger implicit suspension (e.g. viaconfiguration of a suspension timer value) or the eNB 102 a can chooseto send the explicit RRC Connection suspend message. eNB 102 a may alsochoose to configure the UE 101 such that RRC suspension procedures orcomponents of the RRC suspension behaviours are either allowed ordisallowed.

Processes Handling Mobility During RRC Connection Suspension

On suspension of a UE's RRC connection, the UE 101 performs cellselection and reselection in a similar manner to that of a normal idlemode UE 101 (i.e. the UE 101 follows the general mobility procedures of3GPP TS 36.304). However, if location-based validity criteria are used,then the UE 101 can be aware when the UE 101 selects/reselects a cell inwhich its suspended RRC Connection is not valid (e.g. a cell where thesuspended RRC context may not be reactivated or re-established).

An example is shown in FIG. 9 where the UE 101 is initially on Cell Aunder eNB1 102 a (point 1). The RRC Connection is suspended. The UE 101reselects from Cell A, under eNB1 102 a, to Cell B, also under eNB1 102a (point 2). It is possible that cells A and B lie within the validityarea, and cell C lies outside the validity area. As the UE moves fromcell A to cell B, from the location based validity criteria, the UE 101knows that its suspended RRC Connection is still valid and hence needtake no action. The UE 101 then reselects from Cell B to Cell C which isunder a different eNB, i.e. eNB2 102 b (point 3). From the locationbased validity criteria, the UE 101 knows that its suspended RRCConnection is no longer valid at point 3. At this point (crossing avalidity area boundary), there are two main alternative mobilityhandling processes for how the UE 101 acts during RRC connectionsuspension. The UE 101 may be configured to only perform one of thefollowing methods, or selectively perform either method.

-   -   obility Alternative A—Do not Inform the Network that the UE is        Outside of the Area where its Suspended RRC Connection is Valid    -   Although at point 3 the UE 101 is aware that it is outside the        area where it knows its suspended RRC Connection is valid, the        UE 101 does not initiate any signalling towards the network.        Instead, the UE 101 continues to perform UE-based mobility and        paging reception procedures and continues to keep its stored RRC        Context Information. In mobility alternative A, as long as the        UE 101 remains within a registered tracking area (TA) of cells        then cell reselections do not trigger any signalling towards the        network (i.e. the network is not made aware of the        reselections). However, the UE 101 would still need to perform a        Tracking Area Update (TAU) if it moved outside of its registered        TA(s), just as it would have to do if it were in idle mode. A TA        would typically cover many cells and many eNBs 102 a,b, . . . n.        The RRC Context Information remains stored in the UE 101 and one        or more RAN or CN nodes such as eNB 102, eNB 102 b, or MME 103        b, so that parts or all of it can potentially be used if, at the        time that data activity is resumed, the UE 101 has returned to a        cell where the suspended RRC Connection is valid. Depending on        the validity area, the cell or eNB on which the suspended RRC        connection is reactivated may be the same or different to the        cell or eNB on which the RRC connection was last suspended.

Mobility Alternative B—Inform the Network that the UE is Outside theArea where its Suspended RRC Connection is Valid

-   -   When, at point 3, the UE 101 is aware that it is outside the        area where it knows its suspended RRC Connection is valid, the        UE 101 in this alternative initiates some signalling to inform        the network. Under mobility alternative B, the signalling        procedures adopted by the UE 101 can, for example, be one of the        following three variants:

Signalling Variant 1—Discard Suspended RRC Connection, Perform NASProcedure and Return to Idle.

-   -   On the new cell under eNB2 102 b, in this variant the UE 101        discards its suspended RRC connection and performs signalling by        initiating a Non Access Stratum (NAS) procedure (e.g. an LTE        ‘TAU’ procedure). This may be an unmodified TAU procedure or may        be a TAU procedure modified to include a cause value indicating        the reason for sending the TAU (i.e. the UE has identified that        the suspended RRC connection is no longer valid). This TAU        procedure causes the MME 103 b to release the S1 connection to        eNB1 102 a and the eNB1 102 a to release the suspended RRC        Connection. At completion of the TAU procedure the UE 101 is        placed into idle mode and hence has no RRC Connection with any        eNB 102 a,b . . . n.

Signalling Variant 2—Discard Suspended RRC Connection, Perform NASProcedure and Remain RRC Connected.

-   -   On the new cell under eNB2 102 b, in this variant the UE 101        discards its suspended RRC connection and performs signalling by        initiating a NAS procedure (e.g. TAU or Service Request). This        may be an unmodified TAU or Service Request or may be a modified        TAU or service request modified to include a cause value        indicating the reason for initiating the procedure (i.e. the UE        has identified that the suspended RRC connection is no longer        valid). This TAU/Service Request causes the MME 103 b to release        the S1 connection to eNB1 102 a and causes eNB1 102 a to release        the suspended RRC Connection. The MME 103 b initiates new access        stratum security and establishment of data radio bearers (DRBs)        and establishment of an S1 user plane connection to eNB2 102 b.        At completion of the TAU/Service Request, the UE 101 remains in        RRC Connected with eNB2 102 b. The eNB2 102 b may choose to        suspend the RRC Connection as described above, such that the new        RRC connection between the UE 101 and eNB2 102 b is suspended.        If so, the state of the UE 101 at point 3 in FIG. 9 would then        be the same as it was at point 1 but with an RRC Connection with        eNB2 102 b instead of eNB1 102 a.

Signalling Variant 3—Maintain Suspended RRC Connection, PerformSignalling to Inform CN of Mobility

-   -   On the new cell under eNB2 102 b, in this variant the UE 101        maintains its suspended RRC context and performs signalling by        initiating a procedure in order to inform the CN 103 that the UE        101 has a currently-invalid suspended RRC Connection. This        procedure could be a NAS procedure—for example, it could be an        unmodified TAU or a TAU containing a new indication that the UE        101 has an invalid suspended RRC Connection, or it could be a        new NAS message such as “NAS Mobility Update” message.        Alternatively, this could be an access stratum (AS) procedure        that in turn triggers the eNB2 102 b to inform the CN 103 that        the UE 101 has a suspended-but-currently-invalid RRC        connection—for example it could be an new “RRC Mobility Update”        message sent from UE to eNB2 102 b, or it could be an existing        RRC message containing a new “Mobility Update Indicator”, then        followed by an “S1 Mobility Update” message from eNB2 102 b to        MME 103 b. Whatever form the signalling takes the purpose of the        procedure is that it will cause the S-GW 103 a to suspend the S1        user plane. At completion of the procedure the UE 101 remains        with its suspended RRC connection but is camped on eNB1 102 a.        Note that in order to perform the TAU procedure the UE may or        may not have had to create an RRC Connection with eNB2 102 b and        an S1 connection with the MME 103 b. If such connections do need        to be created, this may be considered as a temporary RRC        Connection that gets discarded at the completion of the TAU or        other update message. If the MME 103 b were to establish access        stratum security and establish DRBs then this temporary RRC        Connection would become the ‘permanent’ RRC Connection and the        suspended RRC Connection would be discarded.        Mobility within the Validity Area        Mobility alternatives A and B describe example procedures        associated with UE mobility events that cross the validity area        boundary (i.e. as the UE transitions in or out of the validity        area). Other procedures are possible. There are also a set of        possible mobility alternatives associated with the UE's mobility        between cells within a validity area. These ‘intra-area mobility        procedures’ may optionally be employed in addition to the        procedures concerned with mobility across validity area        boundaries.        In a first intra-area alternative, the UE performs signalling to        inform the RAN and/or CN of the UE's mobility within the        validity area. This can be used to allow a previously-suspended        RRC connection to be migrated between an old and a new cell in        accordance with the UE's mobility from the old cell to the new        cell. The old and new cells may be controlled by the same eNB        and MME, or they may be controlled by different respective old        and new eNBs, or different respective old and new MMEs. With        further reference to FIG. 9, it is possible that cells A, B and        C all lie within the validity area. In this case, and when        operating according to the first intra-area mobility        alternative, when the UE reselects to Cell C (under eNB2 102 b)        the UE 101 communicates with eNB2 102 b, informing it of the        UE's presence within the cell. This may take the form of an RRC        re-establishment procedure or may comprise a new mobility update        procedure, or a modified version of an existing mobility        procedure, for example procedures based on or comprising        handover-related signalling. Although eNB2 102 b lies within the        validity area, it may or may not yet be in possession of RRC        context data related to the suspended RRC context for UE 101.        This will depend on whether eNB1 102 a has forwarded the RRC        context data to eNB2 102 b prior to the UE's reselection to        Cell C. This forwarding of the RRC context data from eNB1 102 a        to eNB2 102 b may be achieved through the use of handover        preparation signalling such as Handover Request (from eNB1 to        eNB2) and Handover Request Acknowledge (from eNB2 to eNB1)        messages (and this is shown in FIG. 23 step (10) and FIG. 26        step (8) as the optional preparation of other eNBs over X2). If        eNB2 102 b is not in possession of the RRC context data for UE        101, it may attempt to retrieve the RRC context data from        another node within the RAN 102 (such as eNB1 102 a) or from a        node within CN 103 (such as MME 103 b). Signalling procedures        between eNB2 102 b and the other node(s) such as eNB1 102 a or        MME 103 b are used to retrieve the RRC context data for UE 101        via network interfaces between those RAN and CN nodes. The        retrieval of the RRC context from eNB1 102 a by eNB2 102 b may        be achieved through the use of context retrieval signalling such        as the RLF Indication message (from eNB1 to eNB2), the Handover        Request message (from eNB1 to eNB2) and Handover Request        Acknowledge message (from eNB2 to eNB1). An example of context        retrieval signalling between eNBs is shown in FIG. 28 steps (4b)        and (6) and an example of context retrieval signalling between        an eNB and an MME is shown in FIG. 28 step (5). as eNB2 102 b        may also communicate with CN nodes such as MME 103 b and/or S-GW        103 a in order to switch the path of an active or suspended S1        connection associated with UE 101 such that it now terminates at        eNB2 102 b instead of at eNB 102 a. If eNB2 102 b wishes to        accept the connection with the UE, eNB 102 b communicates with        UE 101 either to command or confirm reactivation or        re-establishment of the RRC connection within Cell C (in this        case the RRC connection resumes from suspension), or to simply        confirm or acknowledge the mobility event to UE 101 (in which        case the RRC connection may thereafter return to a suspended        state following the successful transfer of the UE context to        Cell C under eNB2 102 b).

In the first intra-area mobility alternative, the RAN is informed eachtime the UE reselects another cell within the validity area. Thiscarries the advantage that the network may switch the S1 connection(from the core network to the RAN) to the correct RAN node (eNB) inorder to track the UE's mobility. Thus, inbound downlink data destinedfor the UE may always be routed (via S1) to the correct eNB anddelivered to the UE, thereby avoiding the need to first page the UEacross a wider area to determine its current cell or location. In asecond intra-area mobility alternative the UE may not inform the RAN orCN at the time of a cell reselection within the validity area. Instead,the UE may wait until there is a need for user plane data beforecommunicating with the eNB controlling the cell on which the UE iscurrently camped. In such cases, the UE may attempt to reactivate orre-establish a suspended RRC connection on the currently-camped cell ifit lies within the validity area. If the eNB in control of thecurrently-camped cell is not in possession of the stored RRC contextdata for UE 101, it would again need to invoke procedures for RRCcontext retrieval from another node, in a similar manner to thosedescribed for the first intra-area mobility alternative. Whilst thissecond intra-area mobility alternative carries some advantage in thatmobility signalling (to move the suspended RRC connection to a new cell)may be avoided at each cell reselection event, it also carries thedisadvantage that in the event of inbound downlink data destined for theUE, the network may not have up-to-date information regarding thecurrent cell or location of the UE. Thus, the UE may need to be paged inother cells before the data can be delivered.

Example message sequence charts for the three signalling variants (1, 2,3) for mobility across a validity area boundary are shown in FIG. 10,FIG. 11, and FIG. 12 respectively. The initial steps of these charts arethe same with the differences between the three variants occurringwithin the areas identified by rectangles having rounded ends.

Signalling variant 1, shown in FIG. 10, can be described as follows.

-   -   1. The UE 101 initially has a suspended RRC Connection with eNB1        102 a.    -   2. UE 101 performs cell reselection to a cell under the control        of eNB2 102 b    -   3. Following cell reselection the UE 101 determines that it is        now in a cell where its suspended RRC Connection may not be        valid.    -   4. The UE 101 releases its suspended RRC Connection for eNB1 102        a. UE 101 enters idle mode.    -   5. The UE 101 initiates a TAU. To perform the TAU the UE 101        first establishes an RRC Connection with eNB2 102 b and then        sends the Tracking Area Update Request. The MME 103 b responds        with a Tracking Area Update Accept.    -   6. Following the completion of the TAU procedure, the UE 101        returns back to idle mode.    -   7. The MME 103 b also sends an S1 release command to eNB1 102 a        to inform it that it can release its suspended RRC Connection        for the UE 101 and/or release any active or suspended S1        connections for the UE 101.        Signalling variant 2, shown in FIG. 11, can be described as        follows.    -   1. The UE 101 initially has a suspended RRC Connection with eNB1        102 a.    -   2. UE 101 performs cell reselection to a cell under the control        of eNB2 102 b.    -   3. Following the cell reselection, the UE 101 determines that it        is now in a cell where its suspended RRC Connection may not be        valid.    -   4. The UE 101 releases its suspended RRC Connection for eNB1 102        a. UE 101 enters idle mode.    -   5. The UE 101 initiates a TAU or Service Request procedure. To        perform the TAU or Service Request procedure the UE 101 first        establishes an RRC Connection with eNB2 102 b and then sends the        Tracking Area Update Request or Service Request. The MME 103 b        responds by triggering the establishment of access stratum        security and the establishment of the DRBs and the S1 user plane        with eNB2 102 b. The figure shows the Service Request procedure        although the TAU procedure would be quite similar. Note the        figure does not label the individual messages that make up the        overall procedure.    -   6. Following the completion of the TAU or Service Request        procedure, the UE remains in RRC Connected with eNB2 102 b.    -   7. The MME 103 b also sends an S1 release command to eNB1 102 a        to inform it that it can release its suspended RRC Connection        for the UE 101 and/or release any active or suspended S1        connections for the UE 101.        Signalling variant 3, shown in FIG. 12, can be described as        follows.    -   1. The UE 101 initially has a suspended RRC Connection with eNB1        102 a.    -   2. UE 101 performs cell reselection to a cell under the control        of eNB2 102 b.    -   3. Following the cell reselection, the UE 101 determines that it        is now in a cell where its suspended RRC Connection may not be        valid.    -   4. The UE 101 maintains its suspended RRC Connection for eNB1        102 a.    -   5. The UE 101 initiates signalling to inform the CN 103 that the        UE 101 has a suspended RRC Connection but has moved outside the        area where its suspended RRC Connection is known to be valid.        The example in FIG. 12 shows the UE 101 establishing a        ‘temporary’ RRC Connection and in the RRC Connection Setup        Complete message the UE 101 includes a ‘Mobility Update        Indicator’ although other alternatives are possible including        the use of a TAU procedure (in which case signalling variant 3        is similar to signalling variant 1 with the exception that the        suspended RRC connection is maintained following the UEs        reselection to a cell under control of eNB2 102 b and is not        released—i.e. the procedure is as per signalling variant 1 but        without execution of steps 4, 6 and 7).    -   6. From reception of the Mobility Update Indicator the eNB2 102        b is aware of the purpose of this RRC Connection Establishment        and sends an S1 Mobility Update message to the MME 103 b. In        response to this the MME 103 b sends an S1 user plane suspend        message to the S-GW 103 a.    -   7. On receipt of the S1 user plane suspend message the S-GW 103        a knows that DL data for this UE 101 should be buffered, and the        UE 101 located before the data can be delivered (i.e. the S-GW        103 a should not simply forward the DL data over the S1 to eNB1        102 a as there is a possibility that the UE 101 will not be        located under eNB1 102 a).    -   8. eNB2 102 b instructs the UE 101 to release the ‘temporary’        RRC Connection. The UE 101 still maintains its suspended RRC        connection for eNB1 102 a but is camped on a cell under eNB2 102        b.

For mobility across a validity area boundary, a consequence of bothsignalling variants 1 and 2 is that the UE 101 releases the suspendedRRC Connection and initiates a signalling procedure as soon as it movesout of the area where the suspended RRC Connection is known to be valid.Whenever data activity resumes, it will be necessary for a new RRCConnection (and Security and DRBs) to be established before datatransfer can begin. Therefore signalling variants 1 and 2 may not bevery effective at reducing signalling load if the UE is moving.

A benefit of signalling variant 3 compared to variants 1 and 2 isfurther explained by reference to FIG. 13, which shows a mobilityscenario similar to that shown in FIG. 9, in which a UE 101 with asuspended RRC connection moves out of its cell to a point 3 in anothercell in which the RRC connection is invalid, but the FIG. 13 scenarioadditionally shows the UE 101 moving to points 4 and 5. As explainedabove, with signalling variant 3 at point 3 the UE 101 has a suspendedRRC Connection associated with eNB1 102 a and has signalled to thenetwork that it has moved to out of the area where it knows itssuspended RRC Connection is valid. The S-GW 103 a has suspended the S1user plane to eNB1 102 a.

In the FIG. 13 mobility scenario, after moving to point 4 the UE 101reselects back to cell B which is under the control of eNB1 102 a. Nosignalling needs to be initiated towards the network. If data activitywere to resume at this point, then the suspended RRC Connection witheNB1 102 a could be reactivated. Similarly, the S1 connection betweenSGW 103 a and eNB1 102 a could also be reactivated if it had beenpreviously suspended.

In the FIG. 13 mobility scenario, after moving to point 5 whilst the RRCconnection with eNB1 102 a remains suspended, the UE 101 reselects backto cell C which is under the control of eNB2 102 b. Although the UE 101is again moving outside the area where it knows its suspended RRCConnection is valid, there is no need to initiate any signalling. Thisis because the S1 user plane connection between SGW 103 a and eNB1 102 ahas already been suspended at the S-GW 103 a (this having occurred onthe transition from point 2 to point 3). If data activity were to resumeat this point, then the suspended RRC Connection with eNB1 102 a wouldbe released and a new RRC Connection would need to be established witheNB2 102 b.

It can be seen that with signalling variant 3, signalling towards thenetwork is only required the first time that the UE 101 moves out of thearea where it knows that its suspended RRC Connection is valid, andwhilst the RRC connection remains suspended, subsequent moves in and outof the area can be performed without any signalling. Hence, thisapproach is effective at reducing signalling that may otherwise beassociated with a UE 101 that is located close to a boundary of 2 cellswhere ‘ping-pong’ reselections between the cells could occur.

As an extension to signalling variant 3, the UE could be configured toadditionally perform signalling towards a RAN or CN node whenever itmoves back in to a cell or group of cells for which the suspended RRCconnection is again valid (e.g. a cell under the control of eNB1 102 a).This could enable a suspended S1 connection between SGW 103 a and eNB1102 a to be reactivated.

The above procedures may be supplemented with timer based expiry of asuspended RRC connection. For example, a timer may be started at thetime of suspension, or at the time of leaving a suspension cell (orgroup of cells). When the timer expires, the UE 101 (and eNB 102 a,b . .. n and CN 103 nodes) discard any UE 101 context information and the UE101 returns to normal idle mode operation. If common timers are usedwithin both the UE 101 and the eNB 102 a,b . . . n or CN 103 nodes) thismay take place without any signalling between the UE 101 and the any ofthe RAN or CN nodes. If the timers are implemented only at the eNB 102a,b . . . n or CN 103 node side, signalling may be required for the RANor CN nodes to inform the UE that the suspended RRC connection is beingreleased and to instruct a return to idle.

Some possibilities within the signalling variants rely on the use ofexisting procedures (NAS Service Request and TAU) and hence the UE 101can assume that these are supported by the network. However, otherpossibilities within the signalling variants rely on new signallingfunctionality. In such cases, it may be necessary for the UE 101 to knowthat the eNB2 102 b supports the new signalling before it initiates thatsignalling towards the eNB2 102 b. To address this, eNB2 102 b maybroadcast a support indicator in system information. This could be ageneral indicator to indicate support for all the RRC Connectionsuspension functionality or it could just indicate support for the newsignalling functionality (such as the Mobility Update signalling optiondescribed in FIG. 12 for signalling variant 3). If the UE 101 sees thatthe eNB2 102 b does not support the functionality then the UE 101 canfall back to behaving in line with signalling variants that do notrequire new signalling functionality (e.g. the UE could release itssuspended RRC connection and then initiate a TAU or Service Requestprocedure).

In the present disclosure, ‘releasing an RRC connection’ may mean simplyignoring the stored RRC context data, or indicating or marking that dataas being released or invalid, or scrubbing that data, or deleting thedata from memory. Other methods that achieve the same functional effectof releasing an RRC connection are also intended to be within the scopeof the present disclosure.

Handling Receipt of Downlink (DL) Data During RRC Connection Suspension

On suspension of a UE's RRC connection, the UE 101 may perform cellselection and reselection in a similar manner to that of a normal idlemode UE 101 (i.e. the UE 101 follows the general mobility procedures of3GPP TS 36.304). In addition, the UE 101 may monitor the paging channelin exactly the same way as it does in idle mode; i.e. the UE 101 willpower on its receiver at the appropriate paging occasions to attempt toreceive a paging message and then check that paging message for the UE'sidentity (e.g. S-TMSI). On reception of a paging message containing theUE's identity, the UE 101 will attempt to resume its suspended RRCConnection as described below.

When DL data arrives in the network for a UE 101 that has a suspendedRRC Connection, it is necessary that the network can contact or page theUE 101 irrespective of which cell the UE 101 may now be located in.Depending on whether RRC Connection Suspension alternative A or B(described above) is used, and whether Mobility alternative A or B (alsodescribed above) is used, then different scenarios for paging the UE 101when DL data arrives at the S-GW 103 a are possible. Three scenarios forhandling DL data in the network will thus now be described withreference to FIGS. 14 to 16. FIG. 14 shows a message sequence chartrepresenting a method of handling DL data in the network when the UE 101has a suspended RRC Connection with eNB1 102 a. The UE 101 is currentlylocated on a cell under eNB1 102 a and the 51 user plane between SGW 103a and eNB1 102 a is not suspended (1). When DL data arrives at the S-GW103 a (2), the S-GW 103 a forwards the user plane data directly to eNB1102 a (3). This is normal S-GW 103 a behaviour for a UE 101 in RRCConnected state. eNB1 102 a buffers the DL data (4) and then sends apaging message or notification of data arrival message to the UE 101(5). When the UE 101 responds to the paging/notification, (e.g. via thesending of an RRC re-activation request) the suspended RRC Connectionmay be reactivated and then the eNB1 102 a will be able to deliver theDL data. FIG. 15 shows a message sequence chart representing a method ofhandling DL data in the network when the UE 101 has a suspended RRCConnection with eNB1 102 a. The UE is currently located on a cell undera different eNB (i.e. eNB2 102 b) and the S1 user plane between SGW 103a and eNB1 102 a is not suspended (1). When DL data arrives at the S-GW103 a (2), the S-GW 103 a forwards the user plane data directly to eNB1102 a (3). This is normal S-GW 103 a behaviour for a UE 101 in RRCConnected. The S-GW 103 a is not aware that the UE 101 has moved or mayhave moved away from eNB1 102 a and hence the S-GW 103 a is not able totake any alternative action. eNB1 102 a buffers the DL data (4) and thensends a paging message or notification of data arrival message to the UE101 (5). As the UE 101 is no longer located in a cell under eNB1 then noresponse (in the form of an attempt by the UE to reactivate thesuspended RRC Connection) is received (6). eNB1 102 a sends a “pagingescalation” message to the MME 103 b (7) in order to request the MME 103b to page the UE 101 over a wider group of cells (8) (for example theMME 103 b could page the UE 101 in all the cells of the tracking area(s)(TA(s)) in which the UE 101 is registered).

FIG. 16 shows a message sequence chart representing a method of handlingDL data in the network when the UE 101 has a suspended RRC Connectionwith eNB1 102 a and the S1 user plane connection between SGW 103 a andeNB1 102 a is suspended (1). Note that the S1 user plane suspension mayhave occurred as a result of RRC Connection suspension alternative B oras a result of Mobility alternative B with signalling variant 3. The UE101 may be located in a cell under eNB1 102 a (i.e. the eNB where theRRC Connection was suspended) or it may be located under a cell of adifferent eNB 102 b, . . . n. When DL data arrives at the S-GW 103 a(2), the S-GW 103 a buffers this user plane data (3). The S-GW 103 athen initiates a paging procedure towards the MME 103 b to request theMME 103 b to page the UE 101 (4). MME 103 b then pages the UE 101 over awider group of cells, for example it could page the UE 101 in all thecells of the TA(s) in which the UE 101 is registered.

Handling a Suspended RRC Connection to Resume Uu Data Transfer

RRC Connection Reactivation can be triggered by UL data being generatedin the UE 101, or by the reception of a paging or DL data notificationmessage indicating that the network has DL data waiting to be delivered.When this occurs the UE 101 first determines whether its suspended RRCConnection is valid for the cell in which it is currently located.Depending on whether the suspended RRC Connection is determined to bevalid, a number of different options are possible.

FIG. 17 shows a message sequence chart representing the RRC reactivationmethod for a UE 101 with a suspended RRC Connection with eNB1 102 a (1).The need for an active RRC Connection is triggered by UL data beinggenerated in the UE 101, or by the reception of a paging or DL datanotification message (2). The UE 101 determines that its suspended RRCConnection is valid for the cell on which it is located (3). The UE 101initiates an RRC Connection Reactivation procedure by sending an RRCConnection Reactivation Request (4). On receipt of this message the eNB1102 a checks that it has a valid suspended RRC Connection for this UE101. Optionally (and not shown) it may also invoke procedures toretrieve RRC context data for the UE from another node of the RAN 102 orCN 103, and may communicate with other nodes of the RAN or CN toinitiate a path switch of the S1. If eNB1 102 a has a valid suspendedRRC Connection (or has been able to retrieve one from another node) thenit sends an RRC Connection Reactivation message to the UE 101 (5) andthe UE 101 responds with an RRC Connection Reactivation Complete message(6). The RRC Connection Reactivation message may or may not includeconfiguration updates to one or more of the previously-stored RRCconnection parameters for the UE to use following the reactivation. TheUE 101 can now start to send any user plane data that it may havebuffered (8). If the S1 user plane had been suspended the eNB1 102 a maysend an S1 user plane resume message to the S-GW 103 a (7) (possibly viathe MME 103 b as shown as optional by the dotted lines in FIG. 17) andon receipt of this the S-GW 103 a can resume the S1 user plane and startto forward to the eNB1 102 a any DL user plane data that may be bufferedin the S-GW 103 a (8). As an alternative, and if the S1 connection wassuspended only in the DL direction, the reception of UL user plane datafrom the UE 101 may be used by the S-GW 103 a as an implicit S1 userplane resume message.

FIG. 18 shows a message sequence chart representing another RRCreactivation method for a UE 101 with a suspended RRC Connection witheNB1 102 a (1) but which is no longer valid. The need for an active RRCConnection is triggered by UL data being generated in the UE 101, or bythe reception of a paging or DL data notification message (2). In thiscase, the UE 101 determines that its suspended RRC Connection is notvalid for the cell on which it is located (3) (for example, this may bethe case if the UE 101 is on a cell that does not lie within a specifiedvalidity area, or in the event that a validity timer has expired). TheUE 101 releases its suspended RRC Connection and enters the RRC idlestate (4). The UE 101 then initiates a normal procedure for establishingan RRC Connection towards eNB2 102 b and establishing user plane radiobearers (i.e. the UE initiates NAS Service Request procedure) (5) and oncompletion of this procedure user plane data transfer is possible (6).

FIG. 19 shows a message sequence chart representing another RRCreactivation method for a UE 101 with a suspended RRC Connection (1),which the eNB1 102 a determines is invalid. The need for an active RRCConnection is triggered by UL data being generated in the UE 101, or bythe reception of a paging or DL data notification message (2). The UE101 determines that its suspended RRC Connection is valid for the cellon which it is located (3). The UE 101 initiates an RRC ConnectionReactivation procedure by sending an RRC Connection Reactivation Request(4). On receipt of this message the eNB1 102 a checks that it has asuspended RRC Connection for this UE 101 and may also check whether allrequired parameters of the stored RRC connection remain valid.Optionally (and not shown) eNB1 102 a may also invoke procedures toretrieve RRC context data for the UE from another node of the RAN 102 orCN 103. In FIG. 19, the eNB1 102 a determines that it does not have asuspended RRC Connection for the UE 101 or that some of the stored RRCconnection parameters are invalid (5). This may be due, for example, toexpiry of a validity timer in the eNB1 102 a. Alternatively, it may bedue to eNB1 102 a having assigned some of the resources associated withthe suspended RRC connection to another UE, or due to eNB1 102 aotherwise determining that for any valid reason, parts or all of thesuspended RRC connection are no longer valid. In a further alternative,it may due to the UE 101 accessing an eNB that is different from the onewhich has the UE's suspended RRC Connection and a failure of eNB1 102 ato retrieve the RRC context data from the other eNB. The eNB1 102 aresponds with an RRC Connection Reactivation Reject message (6). The UE101 releases its suspended RRC Connection and enters RRC idle mode (7).The UE 101 then initiates a normal procedure for establishing an RRCConnection and establishing user plane radio bearers (i.e. the UE 101initiates a NAS Service Request procedure) (8) and on completion of thisprocedure user plane data transfer is possible (9).

It may be necessary for the UE 101 to know that the eNB 102 a,b . . . nsupports the new signalling RRC Connection ReactivationRequest/Setup/Reject signalling before it initiates that signallingtowards the eNB 102 a,b . . . n. To address this, an eNB 102 a,b . . . nmay broadcast a support indicator in system information. This could be ageneral indicator to indicate support for all the RRC Connectionsuspension functionality or it could just indicate support for theRequest/Setup/Reject signalling. If the UE 101 sees that the eNB 102 a,b. . . n does not support the functionality then the UE 101 would releaseits suspended RRC connection and then initiate a Service Requestprocedure.

An alternative to the eNB 102 a,b . . . n broadcasting a supportindicator would be for the eNB 102 a,b . . . n that initially suspendsthe UE's RRC Connection to set the area based validity criteria in a wayto ensure that the UE 101 only attempts to reactivate a suspended RRCConnection on a cell/eNB 102 a,b . . . n that is known to support thefunctionality. In the simplest case the eNB 102 a,b . . . n thatsuspends the UE's RRC Connection would only include in the validitycriteria cells that are located under the same eNB 102 a,b . . . n.However, the validity area may in general span cells controlled bydifferent eNBs.

There are many ways to combine the various RRC Connection Suspension andMobility scenarios described above. Table 2 below provides four possiblecombinations but it is to be noted that other combinations orsub-combinations are possible. In the examples of Table 2, combinationsof RRC Connection Suspension Alternatives A or B with MobilityAlternatives A or B are discussed. For each combination, Table 2describes in what status the RRC Connection and the S1 user planeconnection would reside at various points in time. The status of the RRCConnection and S1 user plane may be:

-   -   idle—no RRC Connection exits, no S1 user plane is established    -   eNB1/2—an RRC Connection exists with eNB1 or eNB2, an S1 user        plane is established between S-GW and eNB1 or eNB2    -   Suspended (eNB1)—a suspended RRC Connection exists with eNB1,        the S1 user plane between S-GW and eNB1 is suspended        The columns of the table T0-T2 relate to different        times/instances and are defined with reference to FIG. 9.    -   T0—UE 101 in location 1 of FIG. 9, before RRC Connection is        suspended    -   T1—UE 101 in location 1 (or location 2, if the UE 101 has        performed cell reselection) of FIG. 9, after RRC Connection is        suspended    -   T2—UE 101 in location 3 of FIG. 9.

TABLE 2 T2 (move to cell under eNB2 Combination Connection T0 T1 whilesuspended) 1/ S1 eNB1 eNB1 eNB1 RRC Sus Alt A, RRC eNB1 SuspendedSuspended Mobility Alt A (eNB1) (eNB1) 2/ S1 eNB1 Suspended SuspendedRRC Sus Alt B, (eNB1) (eNB1) Mobility Alt A RRC eNB1 Suspended Suspended(eNB1) (eNB1) 3/ S1 eNB1 eNB1 idle/eNB2/ RRC Sus Alt A, SuspendedMobility Alt B (eNB1) RRC eNB1 Suspended idle/eNB2/ (eNB1) Suspended(eNB1) 4/ S1 eNB1 Suspended idle/eNB2/ RRC Sus Alt B, (eNB1) SuspendedMobility Alt B (eNB1) RRC eNB1 Suspended idle/eNB2/ (eNB1) Suspended(eNB1)

In this example, it should be noted that, for combinations 3 and 4 shownin Table 2, three possible cases are shown for the condition of the RRCand S1 connections corresponding to the signalling variants 1/2/3respectively which may be adopted within Mobility Alternative B.

In addition, it should be noted that combination 4, which corresponds toRRC Connection Suspend alternative B and Mobility alternative B, isshown in the table for completeness. However, with this alternative theS1 user plane is suspended as soon as the RRC Connection is suspended,meaning that any DL data will be buffered at the S-GW 103 a until the UE101 has been paged/notified and has reactivated its RRC Connection. Thusthere may be little benefit to performing any signalling when the UE 101moves to a cell under a different eNB 102 a,b, . . . n.

Given that the various possible processes for handling an RRC connectionsuspension in accordance with the present disclosure have been describedabove, a number of example scenarios will now be described showing howthese various suspended RRC connection handling procedures can operatetogether.

Example Scenario 1

FIG. 20 shows a message sequence chart representing a possible handlingof the suspension and later attempted reactivation of an RRC connectionbetween UE 101 and a RAN 102 in which (at the time of the reactivationattempt) the UE 101 has moved out of the cell(s) where the suspended RRCconnection is valid in accordance with suspension alternative A (CN notinformed of the RRC suspension) and mobility alternative A (network notinformed of mobility) described above. Due to this processing, the CN103 is not aware that the RRC connection is suspended and hence the S1connection is not suspended. When DL data arrives at the network, thenetwork does not know for certain the cell in which the UE 101 iscurrently located, nor does it know whether any suspended RRC context isvalid. The S1 connection is not suspended and remains active, hence DLdata incident at SGW 103 a is forwarded via S1 to eNB1 102 a. eNB1 102 aattempts to contact the UE 101 via transmission of a paging message andin the absence of a response, a paging escalation approach is used inorder to contact the UE 101. The suspended RRC Connection is not validin the cell in which the UE 101 is found and so it is released and afresh RRC Connection is established for the data to be delivered.

With reference to FIG. 20, the steps of the sequence in this scenarioare:

-   -   1. UE 101 is initially in RRC connected with user plane bearers        established such that it is possible for user data to be        transferred between UE 101 and S-GW 103 a and then on to the        P-GW 103 c (not shown in FIG. 20) and beyond.    -   2. Criteria to trigger suspension are met and eNB-1 102 a        decides change the UE 101 to UE-controlled mobility and to        suspend the RRC connection.    -   3. eNB-1 102 a send a message to the UE 101 to instruct it to        enter UE-controlled mobility and to suspend the RRC connection.        For example this message may be called RRC Connection Suspend as        shown in the Figure, or may be called RRC UE controlled mobility        command, or some other suitable name.    -   4. eNB-1 102 a and UE 101 suspend the RRC connection. The UE 101        performs UE-controlled mobility similar to that of idle mode.    -   5. When the UE 101 has suspended the RRC connection and enters        UE-controlled mobility, cell reselections may occur. As long as        the UE 101 remains within a registered TA then these        reselections do not trigger any signalling towards the network        (i.e. the network is not made aware of the reselections in        mobility alternative A). Steps 1-5 (excepting the cell        reselections) are indicated in FIG. 20 in the upper rectangle        having rounded ends.    -   6. After a period, when an RRC connection with UE 101 is once        again needed, in the network-originated case, user plane data        arrives in the S-GW 103 a. S-GW 103 a immediately forwards the        data on the S1 user plane interface to the eNB1 102 a. On        arrival of the user plane data in the eNB1 102 a the eNB1 102 a        sends a paging message to the UE 101 in order to trigger the RRC        Connection Reactivation. However, in this case eNB-1 102 a does        not receive any response to this paging message, and thus eNB-1        102 a can conclude that the UE 101 is no longer located in a        cell under its control. In order to contact the UE 101 that may        be located in a cell under a different eNB 102 b, . . . n the        eNB-1 102 a must escalate the paging, meaning that it must        trigger the MME 103 b to send paging requests to other eNBs 102        b, . . . n to page the UE 101 within the TA(s) in which the UE        101 is currently registered. In this example scenario in FIG. 20        the escalation causes eNB-2 102 b to send a page and this is        successfully received by the UE 101.    -   7. The UE 101 sends the RRC Connection Reactivation Request to        the eNB-2 102 b. As an alternative step 7, the UE 101 may be        able to determine prior to sending the RRC Connection        Reactivation Request to the eNB-2 102 b that the reactivation        attempt will not be successful on this cell. For example the UE        101 may be able to determine this from the Cell ID of the cell,        or eNB ID of the cell or some additional indicator that may be        sent in the paging message. If the UE 101 does determine that        the reactivation will not be successful then the UE 101 does not        transmit RRC Connection Reactivation Request but jumps directly        to step 9.    -   8. Due to the fact that in this case the eNB-2 102 b does not        have the UE's suspended RRC Connection (or is not able to        successfully retrieve it from another node), the eNB-2 102 b        responds with a RRC Connection Reject.    -   9. The UE 101 releases its (suspended) RRC connection and enters        RRC idle mode. The UE 101 then performs a normal RRC Connection        Establishment procedure in order to setup up a new RRC        connection and continue user plane activity.

Example Scenario 2

FIG. 21 shows a message sequence chart representing a possible handlingof the suspension and later reactivation of an RRC connection between UE101 and a RAN 102 in which the UE 101 has initially moved out of thecell(s) where the suspended RRC connection is valid (and may havereselected a number of times) but when the data activity is to beresumed the UE 101 is once again camped on a cell where the suspendedRRC Connection is valid and hence it can be successfully reactivated inaccordance with suspension alternative B and mobility alternative Adescribed above.

In accordance with suspension alternative B (CN is informed of the RRCsuspension) and mobility alternative A (network is not informed ofmobility), if the UE 101 reselects away from the cell (or cells) onwhich the suspended RRC connection is valid, the UE 101 does not performany signalling to inform the network (unless the reselection results inthe UE crossing a TA boundary such that a ‘normal’ TAU is needed). Thuswhen DL data arrives the network does not know for certain the cell inwhich the UE is currently located, hence nor does it know whether anysuspended RRC context is valid.

The steps of the sequence are:

-   -   1. UE 101 is initially in RRC connected with user plane bearers        established such that it is possible for user data be        transferred between UE 101 and S-GW 103 a and then on to the        P-GW 103 c (not shown in FIG. 21) and beyond.    -   2. Criteria triggering a suspension are met and eNB-1 102 a        decides to change the UE 101 to UE-controlled mobility and to        suspend the RRC connection.    -   3. eNB-1 102 a sends a message to the UE 101 to instruct it to        enter UE-controlled mobility and to suspend the RRC connection.        For example this message may be called RRC Connection Suspend as        shown in FIG. 21, or may be called RRC UE-controlled mobility        command, or some other suitable name.    -   4. eNB-1 102 a and UE 101 suspend the RRC connection. The UE 101        performs UE-controlled mobility similar to that of idle mode.    -   5. eNB-1 102 a informs the CN 103 (MME 103 b or S-GW 103 a or        both) about the RRC suspension. The message to inform the CN 103        may be called S1 user plane suspend. On reception of this by the        CN 103, the S1 user plane bearers remain established but are        suspended (user plane transmission ceases) and the S-GW 103 a,        on reception of downlink user plane data, will not immediately        forward that data over the S1 user plane towards the eNB-1 102 a        and will instead buffer the data pending its delivery. The S1        user plane suspension may only affect the way that the S-GW 103        a treats DL user data arriving in the S-GW 103 a. Hence, in this        case it may be considered as just a DL S1 user plane suspension.    -   6. When the UE 101 has suspended the RRC connection and enters        UE-controlled mobility, cell reselections may occur. As long as        the UE 101 remains within a registered TA then these reselection        do not trigger any signalling towards the network (i.e. the        network is not made aware of the reselections). Steps 1-6        (excepting the cell reselections) are shown in FIG. 21 in the        upper rectangle having rounded ends.    -   7. In the network-originating case for data transfer activation        with the UE 101, user plane data arrives in the S-GW 103 a. Due        to the S1 user plane suspension, this user plane data is        buffered at the S-GW 103 a instead of being immediately        forwarded on the S1 user plane interface to the eNB-1 102 a. The        S-GW 103 a then initiates a paging procedure to contact the UE        101 in whichever cell it may be located. This is quite similar        (or identical) to the paging procedure used when the UE 101 is        idle. The paging indication is sent from the S-GW 103 a to the        MME 103 b and to one or more eNBs 102 a,b . . . n located within        the TA(s) in which the UE 101 is registered. The reception of a        paging message in the UE 101 triggers the UE 101 to attempt the        RRC Connection Reactivation. This is shown within the lower        rectangle having rounded ends. In the UE-originating case the        elements in the lower rectangle do not occur and the arrival of        user data in at the UE 101 directly triggers the UE 101 to        attempts the RRC Connection Reactivation.    -   8. The remainder of the steps in FIG. 21 represent the sequence        of events when the UE 101 attempts the RRC Connection        Reactivation on a cell where the associated eNB-1 102 a does        have the UE's suspended RRC Connection (i.e. the eNB does have        the stored UE context information). This cell may be the cell        the UE 101 was on when the RRC connection was suspended or it        may be another cell controlled by the same eNB-1 102 a or it may        be a cell controlled by another eNB but which is in possession        of (or able to retrieve) the necessary RRC context data for the        UE. The UE 101 sends the RRC Connection Reactivation Request to        the eNB-1 102 a.    -   9. Due to the fact that in this case the eNB-1 102 a does have        the UE's suspended RRC Connection, the eNB-1 102 a responds with        an RRC Connection Reactivation. This message may contain some        new or updated parameter values if the eNB-1 102 a wishes to        change any part of the configuration that was previously        suspended, or it may be a very simple ‘continue’ message (e.g.        without any parameter or configuration updates).    -   10. The UE 101 responds with an RRC Connection Reactivation        Complete. This is an optional step, only needed if the eNB-1 102        a requires extra assurance that the RRC Connection Reactivation        has been successful. In the UE-originated case, uplink user data        from the UE may start to be transmitted as soon as the RRC        Connection Reactivation has been received.    -   11. The eNB-1 102 a informs the CN 103 (MME 103 b or SGW 103 a        or both) that the S1 user plane can continue. This may be an        explicit message as shown in FIG. 21. Alternatively, in the        UE-originated case, and in the case that only the DL of the S1        was originally suspended, uplink user data from the UE 101 sent        from eNB-1 102 a to S-GW 103 a may be considered as an implicit        ‘continue’ command by SGW 103 a.    -   12. On reception of the indication to continue the S1 user        plane, the S-GW 103 a will stop buffering the downlink user        plane data and will forward it over the reactivated S1 user        plane to the eNB-1 102 a for transmission to the UE 101.

Example Scenario 3

FIG. 22 shows a message sequence chart representing a possible handlingof the suspension and later reactivation of an RRC connection between UE101 and a RAN 102. The CN 103 is not informed of the RRC suspension, butthe UE 101 does inform the CN 103 when it moves out of the cell(s) wherethe RRC connection is valid, in accordance with suspension alternative Aand mobility alternative B described above.

In summary this shows the method carried out when the UE 101 has movedout of the cell(s) where the suspended RRC connection is valid, and hasinformed the CN 103 about moving out of the suspension cells via amobility update message so that the S1 is then suspended. When DL dataarrives at the network the UE 101 is paged, the suspended RRC Connectionis not valid in the cell and so it is released and a fresh RRCConnection is established for the data to be delivered.

In this case the CN 103 does not initially know that the UE's RRCconnection has been suspended. A validity indicator may however still bemaintained in the CN 103 for each connected mode UE 101. This indicatormay be set based upon location update information known to the CN 103(e.g. the MME 103 b). Whilst in the connected mode, the CN 103 expectsthat UE 101 mobility events (for example to another cell or eNB 102 b, .. . n) result in a corresponding handover of the S1-U and S1-MME bearersto that eNB. Tracking area updates are expected only from idle mode UEs.Whilst the validity criteria are met, the CN 103 continues to behave asnormal for a connected mode UE 101.

The use of mobility alternative B means that a UE 101 with a suspendedRRC connection (and of which the CN 103 may or may not yet be aware) mayperform autonomous mobility procedures and may be configured to send atracking area update (or other location update) message to the CN 103(e.g. the MME 103 b) in the event that it leaves or re-enters the cell(or group of cells) for which the suspended RRC connection is valid.

If the CN 103 has not been informed at the time of a suspension, the MME103 b initially believes the UE 101 to be still RRC-connected (i.e. notsuspended) unless it learns otherwise. If the UE 101 is configured tosend the additional/augmented mobility messages of mobility alternativeB (e.g. TAU) when suspended, the MME 103 b may subsequently infer fromreceipt of a TAU that the UE's RRC connection has in fact been suspendedand that the UE 101 is currently camped on a cell (or group of cells)for which the suspended RRC connection is not valid. Thus, the MME 103 bis simultaneously and indirectly informed both that the UE's RRCconnection has been suspended and that it is not currently valid. Itwill therefore be appreciated that the signalling ofadditional/augmented mobility messages by the UE 101 may also serve asmessages informing CN nodes (such as MME 103 b and SGW 103 a) of aprevious RRC suspension.

The CN 103 (e.g. MME 103 b) may choose to subsequently suspend the S1connection in such a case. The MME 103 b may optionally reactivate theS1 in the event that it receives a further TAU or mobility message fromthe UE 101 indicating that it has re-entered a cell (or group of cells)for which the suspended RRC connection is once again valid.

Within this example scenario 3 a number of different sub-scenarios arepossible depending on whether the data activity causing a need for anRRC connection is network- or UE-originating, and whether the suspendedRRC connection is still valid at the time a reactivation is required.These different sub-scenarios affect how the wireless communicationsystem handles the processing to resume Uu user plane communications.With reference to FIG. 22, the following describes the processing thatoccurs when the data activity is network-originated and the suspendedRRC connection is invalid at the time of required reactivation.Processing for other sub-scenarios may be derived using logicalcombinations of previously described processing steps and is within thescope of the present disclosure.

-   -   1. During RRC connection suspension (shown in the upper rounded        rectangle) the eNB-1 102 a does not inform the CN 103 of the RRC        suspension and the S1 connection is maintained.    -   2. The UE 101 reselects to a cell assigned to eNB-2 102 b in        which the RRC connection is not valid.    -   3. The UE 101 sends an ‘augmented’ mobility message to MME 103        b, possibly via a temporary RRC connection with eNB-2 102 b, or        via other means not requiring establishment of a temporary RRC        connection with eNB2 102 b (middle rectangle).    -   4. On receipt of the mobility message, MME 103 b sends a message        to S-GW 103 a to suspend the existing S1 connection between SGW        103 a and eNB1 102 a. Thus, the MME 103 b and S-GW 103 a have        been implicitly informed that the RRC connection for UE 101 has        been previously suspended and that the suspended RRC connection        is currently invalid.    -   5. Data addressed to the UE 101 arrives from an external network        104 into the PGW 103 c (not shown in FIG. 22).    -   6. The data is forwarded to the UE's SGW 103 a via the        established S5/8 bearer    -   7. The SGW 103 a and MME 103 b are aware that the RRC connection        for this UE 101 is suspended and data is not able to be        forwarded over the (suspended) S1-U connection. Hence the data        is temporarily buffered by the SGW 103 a.    -   8. The CN 103 (e.g. the MME 103 b) checks its locally-stored        validity status for the suspended RRC connection. For example,        this may involve checking a location validity indicator or a        timer-based validity indicator as previously described    -   9. The CN 103 (e.g. MME 103 b) determines that the suspended RRC        connection is not valid.    -   10. The MME 103 b invokes normal idle-mode RRC connection        establishment procedures:        -   a. The MME 103 b sends a paging request to eNBs 102 a,b . .            . n within the currently-known tracking area location of the            UE 101.        -   b. eNBs 102 a,b, . . . n in receipt of the paging request            send a paging message within cells under their control. The            paging message identifies the UE 101 they are attempting to            contact.        -   c. The UE 101 responds to the page in the cell in which it            is currently camped. The UE 101 responds to the page in the            normal way by initiating a normal RRC connection            establishment procedure.        -   d. The eNB-2 102 b (in conjunction with the MME 103 b)            establishes a new RRC connection with the UE 101 and S1-U            and S1-MME bearers are set up between eNB2 102 b and the SGW            103 a and the MME 103 b respectively    -   11. The data is transferred over the newly-established S1-U from        the SGW 103 a to the eNB-2 102 b (note that the        previously-stored and suspended S1-U may be released)    -   12. The user data is communicated from the eNB-2 102 b to the UE        via the Uu

Example Scenario 4

FIG. 23 shows a message sequence chart representing a possible handlingof the suspension of an RRC connection between UE 101 and a RAN 102. Inthis example suspension is requested by the UE 101 and accepted by thenetwork. In this example the possibility of the eNB 102 a sending theconnection information to other eNBs (not shown) is also envisaged instep 10.

With reference to FIG. 23, the following describes the processing thatoccurs when the suspension request is made by the UE 101:

-   -   1. Initially the UE is assumed to be in RRC_CONNECTED state with        security activated.    -   2. The UE detects that the RRC connection suspension criteria        were met (e.g. either at higher layers, NAS or AS (e.g. RRC)        based on the inputs from user plane entities or application        entities, or based on inactivity timer expiry)    -   3. The UE RRC sends a newly proposed message RRC Connection        Suspend Request (other message names may be used but the intent        of the message is the same) to the eNB. In an alternative        embodiment the UE sends the request message using MAC CE        (control element) signalling.    -   4. It is acceptable to the eNB to suspend the RRC connection,        this is determined either by,        -   a. eNB is independently maintaining a suspension criteria            which is met. This criteria may be based on aspects such as            but not restricted to the following;            -   The traffic activity and trends related to each UE                and/or based on the traffic characteristics per Radio                bearer or application as supported by the UE.            -   Also alternatively or additionally use of local                knowledge pertaining to the device, the application the                application's operation or traffic type therein at the                UE, eNB, S-GW MME or any other associated entity within                the system.) and/or        -   b. eNB requests (and receives) either one-off or periodic            feedback from the MME/S-GW regarding the following:            -   i. While the S1-U connection is being setup between S-GW                and eNB for a UE, eNB can request for a periodic or                threshold-based traffic activity report from S-GW for                the UE. S-GW can subsequently provide the report to the                eNB either periodically or based on the thresholds. Each                report can be for a particular UE or for a group of UEs                for which the report is solicited. The traffic activity                report can contain details like data volumes and trends,                active/inactive period statistics and traffic forecast                related to each UE or other related entity such as per                Radio Bearer or application as supported by the UE.            -   ii. Alternatively S-GW can autonomously send periodic or                threshold based reports to the eNB for every UE with a                S1-U connection at a specified rate.            -   iii. Alternatively when the criteria being maintained by                eNB is met for a UE, it can request a one-off traffic                activity report from the S-GW and make a suspension                decision after evaluating the report from S-GW.    -   5. eNB prepares the source RAN to target RAN containers as it        would do for an Intra-RAT handover, in order to establish the        RRC parameters to store for the UE RRC connection suspension    -   6. eNB optionally stores these containers with appropriate UE        identities attached so that it can be retrieved when required    -   7. eNB optionally sends the prepared containers to MME in a        similar way as would be performed during an existing        handover-via-S1 preparation stage with this additional UE        identity (and or indication of use for RRC Connection        suspension)[2]. These can be sent in a newly proposed explicit        message ‘CIE Context Suspend Request’ along with the eNB and MME        UE identities to uniquely identify the UE.        -   a. eNB can alternatively use one of the existing S1 messages            for handover preparation with a special Information Element            (IE) to indicate that the purpose of the message is for UE            RRC connection suspension    -   8. MME stores the containers along with attached UE identities.        MME either deletes the user plane session at S-GW or suspends        it. S-GW acknowledges MME accordingly    -   9. MME acknowledges the UE context suspension to eNB    -   10. eNB optionally prepares the other eNBs in the vicinity or        all eNBs in the tracking area over the X2-interface with the UEs        context information. This is similar to the existing procedures        defined in [3] for X2 handover preparation. Alternatively a new        X2 message can be defined or an existing message used for        handover can be modified for suspension purposes e.g. by the        additional inclusion of UE identity or an indicator to show that        the container is used for UE suspension.        -   This step enables the neighbouring eNBs to be prepared for            fast re-establishment of the UE RRC context should the UE            move in to their coverage areas. During this preparation            stage, it is proposed that eNBs shall also be provided with            the suspension validity max timer (proposed in section            6.1.6) so that they can delete the stored UE context at the            timer expiry.    -   11. eNB sends a newly proposed ‘RRC connection suspend’ message        to the UE and releases the UE RRC radio resources after        receiving a lower layer L2 RLC acknowledgement from the UE.    -   12. UE receives the connection suspend message and backs up and        stores the same AS configuration as the eNB including the        security configuration and releases the RRC connected state        resources and entities. UE considers itself to be in an        RRC_SUSPENDED state and configures its RRC protocol as if in        RRC_IDLE (but with the stored RRC context) and follows RRC_IDLE        procedures including monitoring paging occasions and using UE        based mobility procedures. In an amended embodiment of this        proposal the paging cycle used by the UE in RRC_SUSPENDED may be        different to that of RRC_IDLE. This may, for example, be to        ensure the UE detects a page indicating user plane data sooner,        by using a shorter paging occasion, this is in order to satisfy        the application QoS for the delivery latency of these packets.    -   13. In one alternative embodiment, the UE would transmit a flag        in the UE capabilities message (this message is described in        3GPP TS 36.331) to indicate that the UE prefers an RRC        Connection to be released in case the eNB chooses not to suspend        the RRC connection. If acceptable to the eNB, it can then follow        the RRC Connection Release procedure (refer section 5.3.8 of TS        36.331) instead of suspending the RRC Connection by way of the        RRC Connection Suspension procedure or leaving the UE with some        or all of its RRC Context whilst behaving as if in RRC IDLE or        alternatively as if not in RRC Connected.

Example Scenario 5

FIG. 24 shows a message sequence chart representing a possible handlingof a suspension request made by the UE 101 of an RRC connection betweenUE 101 and a RAN 102. In this example suspension is not accepted by thenetwork and the network decides to keep the UE in connected mode.

With reference to FIG. 24, the following describes the processing thatoccurs when the suspension request is made by the UE 101.

-   -   1. Initially the UE is assumed to be in RRC_CONNECTED state with        security activated.    -   2. The UE detects that the RRC connection suspension criteria        were met (e.g. either at higher layers, NAS or AS (e.g. RRC)        based on the inputs from user plane entities and application        entities or based on inactivity timer expiry)    -   3. The UE RRC sends a newly proposed message RRC Connection        Suspend Request (other message names may be used but the intent        of the message is the same) to the eNB. In an alternative        embodiment the UE sends the request message using MAC CE        (control element) signalling.    -   4. It is not acceptable for eNB to suspend the RRC connection.        This could result because of one or more of the following        reasons:        -   a. eNB is independently maintaining a suspension criteria            (as described in section 6.1.1 for step 4a) which is not            met; and        -   b. eNB requests (and receives) either one-off or periodic            traffic report feedback from MME/S-GW.    -   5. The eNB sends an RRC Connection suspend reject message        -   a. Optionally the eNB can indicate a back-off or prohibit            timer to the UE so that the UE should not retry the            suspension request whilst the timer is running        -   b. In an alternative embodiment the eNB sends no response            message to the UE, in which case the UE may have a hard            coded back off or prohibit timer which, whilst running,            prevents a further transmission of an RRC Connection Suspend            Request    -   6. The UE continues to remain in RRC CONNECTED state

Example Scenario 6

FIG. 25 shows a message sequence chart representing a possible handlingof a suspension request made by the UE 101 of an RRC connection betweenUE 101 and a RAN 102. In this example suspension is not accepted by thenetwork and the network decides to transition the UE to idle mode.

With reference to FIG. 25, the following describes the processing thatoccurs when the suspension request is made by the UE 101.

-   -   1. Initially the UE is assumed to be in RRC_CONNECTED state with        security activated.    -   2. The UE detects that the RRC connection suspension criteria        were met (e.g. either at higher layers, NAS or AS (e.g. RRC)        based on the inputs from user plane entities and application        entities or based on inactivity timer expiry)    -   3. The UE RRC sends a newly proposed message RRC Connection        Suspend Request to the eNB. In an alternative embodiment the UE        sends the request message using MAC CE (control element)        signalling.    -   4. It is not acceptable for eNB to suspend the RRC connection        and instead the eNB chooses to release the RRC connection, this        could result because of one or more of the following reasons:        -   a. The eNB is independently maintaining release criteria            which are met;        -   b. The eNB requests and gets either one-off or periodic            traffic report feedback from MME/S-GW;        -   c. The eNB determines that it does not want the UE to go to            RRC_SUSPENDED for example due to impending DL user plane            data transmission or by way of internal Radio Resource            Management (RRM) policy; and        -   d. The eNB does not support the functionality and has a            policy to release the RRC connection when incomprehensible            messages are received from the UE.    -   5. The eNB sends an RRC Connection Release message    -   6. The UE receives the message and leaves RRC_CONNECTED state        moving to RRC_IDLE state.

Example Scenario 7

FIG. 26 shows a message sequence chart representing a possible handlingof a suspension request made by the eNB 102 a of an RRC connectionbetween UE 101 and a RAN 102. In this example the UE 101 agrees to havethe connection suspended.

With reference to FIG. 26, the following describes the processing thatoccurs when the suspension request is made by the UE 101.

-   -   1. Initially the UE is assumed to be in RRC_CONNECTED state with        security activated.    -   2. The eNB detects that the RRC connection suspension criteria        were met, this could result for example because:        -   a. The eNB is independently maintaining suspension criteria            which are met and/or        -   b. The eNB requests (and receives) either one-off or            periodic feedback from MME/S-GW    -   3. The eNB prepares the source RAN to target RAN containers as        it would do for an Intra-RAT handover    -   4. The eNB would optionally store these containers with        appropriate UE identities attached so that it can be retrieved        when required    -   5. The eNB optionally sends the prepared containers to the MME        in a similar way as would be performed during an existing        handover-via-S1 preparation stage. These can be sent in a newly        proposed explicit message ‘UE Context Suspend Request’ along        with the eNB and MME UE identities to uniquely identify the UE.        -   a. The eNB can alternatively use one of the existing S1            messages for handover preparation with a special IE to            indicate that the purpose is for UE RRC connection            suspension    -   6. The MME stores the containers along with attached UE        identities. The MME either deletes the user plane session at the        S-GW or suspends it. The S-GW sends an acknowledgement to the        MME accordingly    -   7. The MME acknowledges the UE context suspension to the eNB    -   8. The eNB 102 a optionally prepares the other eNBs in the        vicinity or all eNBs in the tracking area with the UEs context        information over the X2-interface. This is similar to the        existing procedures for X2 handover preparation. Alternatively a        new X2 message can be defined or an existing message for        handover sequence can be modified for suspension purposes.        During this preparation stage, it is proposed that eNBs shall        also be provided with the suspension validity max timer        (proposed in section 6.1.6) so that they can delete the stored        UE context at the timer expiry.    -   9. The eNB sends a newly proposed ‘RRC Connection Suspend’        message to the UE and releases the UE context from the connected        state after receiving a lower layer L2 RLC acknowledgement from        the UE.    -   10. The UE receives the RRC Connection Suspend message and based        on its internal criteria check is happy to suspend the RRC        connection. UE backs up and stores the same AS configuration as        the eNB including the security configuration and releases the        RRC connected state resources and entities. The UE considers        itself to be in an RRC_SUSPENED state and configures its RRC        protocol as if in RRC_IDLE (but with the stored RRC context) and        follows RRC_IDLE procedures including monitoring paging        occasions and using UE based mobility procedures.        -   In an amended embodiment of this proposal the paging cycle            used by the UE in RRC_SUSPENDED may be different to that of            RRC_IDLE. This may, for example, be to ensure the UE detects            a page indicating user plane data sooner, by using a shorter            paging occasion, in order to satisfy the application QoS for            the delivery latency of these packets.    -   11. In an alternative embodiment of this proposal, a scenario is        envisaged wherein UE prefers RRC Connection Release in case of        eNB initiated RRC connection suspension. It is proposed that the        UE would transmit a flag in the UE capabilities that indicates        whether UE prefers a RRC connection to be suspended or released        if the suspension criteria are met on the network side. The eNB        would then suspend/release the RRC connection accordingly.

Example Scenario 8

One possible alternative scenario to scenario 7 would be where uponreceiving an RRC connection suspend message from the eNB, the UE doesnot want to comply with the eNB signal and instead decides to releasethe existing RRC connection and go to RRC_IDLE. This needs additionalsignalling between the UE and the eNB in the form of a subsequent ‘RRCConnection Release Request’ or “RRC Connection Release Indication”.Alternatively the UE may send an RRC Connection Suspend Confirmationmessage with an additional indicator to indicate transition to RRC_IDLEand release of the RRC connection. An alternative embodiment would befor the UE to transmit a flag in the UE capabilities message to indicatethat the UE prefers either an RRC connection to be suspended or releasedif the suspension criteria are met on the network side. The eNB wouldthen suspend/release the connection accordingly (as shown in FIG. 26).

A further alternative upon receiving an RRC connection suspend messagefrom the eNB is where the UE determines that it wants to stay in RRCconnected. This UE based response to the network initiated RRCconnection suspend is considered possible although does not adhere tothe commonly-applied system principle of network-oriented control (i.e.alternative procedures instead allow the UE itself to determine thefinal outcome of the RRC state decision).

Although the UE 101 indicates its preference for suspension or releaseof the RRC connection in an indicator in a RRC Connection ReleaseRequest message or as a flag or some other form of indicator in a UEcapabilities message, the eNB 102 a does not have to follow thisrequest. The eNB 102 a can choose to ignore the request and chooseanother action instead.

Example Scenario 9

In one embodiment it is proposed that the MME acts as the anchor for RRCconnection suspension and that a registered tracking area (TA) or groupsof tracking areas (TAs) act as the boundary for suspension validity.Within the validity area, the UE would treat its suspended RRCconnection context to be valid and the UE or network may initiate areactivation. However other validity areas may be possible. These othervalidity areas may be explicitly configured by eNB or other networkentities, either prior to or at the time of RRC connection suspension,additional signalling may also be required to inform the UEs of theparameters concerning a validity area (for example, a group of Cellglobal identities).

The reason for choosing registered TA (or TAs) as the suspensionvalidity area may be multi-fold:

-   -   a. Any signalling related to RRC connection suspension        continuation/resumption/release can be combined with the        Tracking area update signalling which will anyway take place at        a TA boundary. The additional signalling can be carried either        by modifying the existing messages involved in the TAU procedure        or additional new or existing RRC messages can be piggybacked        over the same RRC connection established for TAU purposes.    -   b. The concept of a TA is already defined in the existing        specifications and therefore adoption of TA requires no        additional specification in terms of validity area definition at        this time. Other validity boundaries may result in some increase        in over the air signalling at the validity area boundaries. This        is in addition to the mandatory TAU signalling that will anyway        happen at TA boundaries.    -   c. A TAU procedure involves the UE, the eNB and the MME and        hence will help the refresh of security configuration and other        UE configuration (e.g. Measurement configuration, dedicated        configuration) at all the relevant entities, thus making it easy        to continue with suspension based on the new configuration at        the end of the TAU        -   i. The base security used for deriving the Access stratum            integrity protection and ciphering are based on Kenb which            is derived at the UE and the MME and differs from eNB to            eNB. Every time there is a connected state cell change (due            to handover or reestablishment or now as proposed for            suspension resumption) keys need to be derived for the            new-eNB. The new keys will not be dependent on the new-eNB            but also on the Kenb used on the source eNB and a network            chaining counter. So a UE simply cannot resume a connection            on any eNB by reusing the security context at the time of            suspension. Instead the security context has to be refreshed            in both the UE and the network entities. Thus refreshing of            the security context (either with a new AS security context            if new connection establishment is needed or with a modified            AS security context if connection reestablishment was used)            will allow the further connection resumption to be            accomplished with lower signalling overhead.

To avoid UEs with suspended connections requesting for reactivation tooquickly, it is also proposed to have an optional inhibit timer such as a‘Minimum Suspension Timer’ which should be obeyed once the UE suspendsan RRC connection. Whilst the timer is running, the UE is prevented frominitiating a reactivation of the suspended connection. This parametercan be specified by eNB in UE dedicated signalling on a per UE basis orfor all UEs simultaneously by sending common signalling in a systembroadcast message. Alternatively this timer shall be configurable by theeNB semi-statically (from time to time) via a new RRC InformationElement (IE) within an existing message or new RRC message, the value ofwhich may be dependant on the QoS delay requirements of the sessionsthat were active at the time of suspension. However the UE need notrespect this timer for all instances, for example the timer may beoverridden when initiating an emergency call.

In a similar way, an optional maximum timer can be specified after whicha suspended connection ceases to be active. Upon expiry of such a timer,the UE and/or eNB could delete the stored UE context information andconsider the suspended connection to be released, and the UE to be innormal RRC IDLE mode.The UE may indicate its support for connection suspension in a UEcapabilities message transferred from the UE to the network where as thenetwork will indicate its support for connection suspension in thebroadcast system information. S1-U behaviourIn the case of both UE-initiated and eNB initiated RRC suspensionprocedures, the MME may request the S-GW to either suspend or delete theS1-U for the UE between S-GW and the serving eNB. In either of thesecases, the downlink traffic destined for the UE will be buffered at theS-GW which will then have to request the MME to page the UE. In responseto the paging, once the UE contacts the MME, it will then have to createor resume the S1-U session for the UE between the S-GW and thenow-serving eNB.If the MME is responsible for paging the UE then it would potentiallyneed to page the UE in all the cells belonging to the registeredtracking area of the UE. This can increase the paging load of the systemas a whole. To manage the paging load there are several schemes as knownto those expert in the field such as:

-   -   the shortest-distance-first scheme (MME first pages in the last        known eNB location of the UE and other locations will be paged        if it elicits no response from the UE),    -   sequential paging (Paging for the UE sequentially in a different        sub-set of eNBs each time).        Two solutions are proposed here to manage the paging load of the        system.        In a first solution, the MME stores the identity of the eNB        which informed the UE context suspension. As proposed        previously, the S1-U session would subsequently be suspended or        deleted. If a need to page the UE arises, the MME can resort to        the shortest-distance-first paging scheme, by using the stored        eNB identity as the last known location of the UE. If this        elicits a response from the UE that would save the MME from        performing a blanket paging for the UE, in all cells of the TA.        In a second solution, it is proposed that at the time of RRC        Connection Suspension, the MME shall keep the S1-U session of        the UE active between the S-GW and the eNB. In this scenario the        downlink user data reaches the eNB on which the RRC Connection        was originally suspended. on arrival of the downlink data, this        eNB then pages the UE thus reducing the system paging load. If        the eNB does not receive any response for the paging, it may        then escalate the paging requirement to the MME which will then        page the UE across all the other eNBs.

Mobility Procedures

Upon suspension of the UE's RRC connection, the UE may perform mobilityprocedures as if it is an idle mode UE. For cell reselections within thevalidity area, the UE may not be required to perform any additionalsignalling until the UE, eNB or MME wishes to resume (or reactivate orre-establish) the RRC connection.The terminology of new-MME and new-eNB is used herein to indicate an MMEand an eNB respectively on which a UE with a suspended RRC contextinitiates signalling either for mobility purposes or for RRC connectionreactivation purposes. These new-MME and new-eNB may be the same as theMME or eNB serving the UE when the RRC connection was suspended or maybe a different eNB and/or MME.If a UE 101 finds itself outside of the suspension validity areaboundary (e.g. one or more TAs), the UE shall perform a tracking areaupdate as per the existing specifications. One representative scenariois depicted in FIG. 27. The details of possible actions in the abovesequence are as follows:

-   -   1. The UE 101 has a valid suspended RRC connection (e.g. the UE        is located in the TA(s) where the RRC connection suspension took        place) and is following idle state mobility procedures.    -   2. Due to its mobility, the UE detects that it is on a cell        which requires a TAU procedure to be performed. The UE also        detects that the suspended RRC connection is no longer valid and        hence locally invalidates the stored RRC context.    -   3. The UE 101 sends an RRC connection request with cause        Mobile-Originated (MO) signalling    -   4. The eNB 102 b sends an RRC connection setup in order to        establish the Signalling Radio Bearer (SRB1)    -   5. The UE 101 sends an RRC connection setup complete message        within which an initial NAS message is contained. The initial        NAS message in this case will be a TAU request.        -   a. Optionally a flag may also be included such as ‘RRC            connection suspension status’ indicating that the UE            previously had a suspended connection. This flag may either            be added as a part of RRC signalling (e.g. RRC Connection            Setup Complete) or as part of NAS signalling (e.g. TAU).        -   b. Optionally, along with or instead of the IE ‘RRC            connection suspension status’, the UE may include another            flag such as ‘RRC suspension continue’ to indicate the            desire to remain suspended after the TAU. The eNB can            initiate the suspension procedure accordingly.    -   6. The eNB 102 b forwards the TAU request to a new MME 103 d and        optionally the ‘RRC connection suspension status’.        -   a. The new eNB 102 b will include the suspension status, if            it wishes to retrieve the suspended RRC configuration from            the old MME 103 a. This suspended RRC configuration may help            the new-eNB to minimize the Over-The-Air (OTA) signalling by            transmitting only a differential configuration to the UE.        -   b. The new eNB 102 b will not include the suspension status            if it wishes to provide a completely new RRC configuration            to the UE, independent of the previous suspended            configuration.    -   7. As is the case for a normal TAU, the new MME 103 d retrieves        the UE context from the old MME 103 b using a UE Context Request        message.        -   a. If received from the UE the new eNB 102 b may send a            corresponding ‘RRC connection suspension status’ flag which            will optionally be added to this UE Context Request as sent            to the old MME 103 b from the new-MME 103 d    -   8. The old MME retrieves the UE context as requested by the new        MME. If the ‘RRC connection suspension status’ flag indicates a        previously suspended RRC connection, it will also retrieve the        stored container available for this UE. Either after a guard        timer expiry or upon confirmation from HSS that the UE location        has changed, the old MME 103 b will indicate to the old S-GW        (not shown) to delete the S1-U session of the UE 101. Upon the        deletion confirmation from the old S-GW, the UE context will be        deleted at the old MME 103 b.    -   9. The old MME 103 b provides the suspended UE context and        optionally the containers to the new MME 103 d as a part of ‘UE        context response’        -   a. The existing ‘UE context response’ message (as used            during TAU) has to be extended to accommodate the newly            proposed optional containers related to the previously            suspended RRC connection.    -   10. The new MME optionally performs NAS level authentication and        security procedures.    -   11. The new eNB 102 b creates a UE session with a new S-GW 103 c        using a ‘Create session request’ message. If there is no change        of S-GW, it will instead be modifying an existing session.    -   12. The new S-GW 103 c acknowledges the session creation    -   13. The new MME 103 d provides the new eNB 102 b with the TAU        accept as well as the newly proposed optional containers        received from the old MME. The MME also provides the security        configuration required to derive the keys for the AS security        procedure. A Bearer setup request may also optionally be issued        by the new MME to the new eNB requiring it to setup a user plane        data bearer for the UE.    -   14. The new eNB performs an AS security activation procedure        with the UE    -   15. The eNB optionally decodes the containers containing the        suspended configuration and will deduce the new differential        reconfiguration that needs to be issued to the UE        -   a. Optionally the eNB may ignore the suspended configuration            and may independently derive a full new configuration that            needs to be issued to the UE.    -   16. The eNB sends an RRC reconfiguration message to the UE which        contains the measurement configuration and the dedicated radio        resource configuration. The TAU accept can be piggybacked onto        this message        -   a. Optionally the eNB may locally refresh the RRC            configuration and perform the remaining TAU procedure on            SRB1 itself.        -   b. Optionally the eNB may include a newly proposed flag in            the RRC reconfiguration message to indicate whether the            configuration being provided is ‘full-config’ or            ‘differential config’. Accordingly the UE is able to            understand whether it should delete the suspended            configuration or reuse it (along with the differential            updates) to derive the new configuration.        -   c. Optionally a mandatory default behaviour can be specified            in the standard as to whether the received configuration            from the eNB should be treated as a full-config or            differential-config.    -   17. The UE applies the received configuration and sends an RRC        connection reconfiguration complete message to the eNB.    -   18. The UE sends a TAU complete message to the eNB which gets        forwarded to the new-MME.    -   19. From this point onwards the RRC connection can again be        suspended based on the suspension procedures described above.        For example, the eNB may initiate a suspension based on the ‘RRC        suspension continue’ flag provided in step 5 above.

Example Scenario 10

UE initiated RRC Connection reactivation within a validity area (eitherautonomously or in response to receipt of a paging signal for downlinkdata) may be achieved by means of RRC Connection Reestablishmentsignalling. RRC Reestablishment signalling procedures are currentlydefined for E-UTRAN for quickly resuming the RRC connection andrestarting the AS security in the case of handover failures or radiolink failures (RLF). The reestablishment procedures allow cells withprepared UE RRC connection data or RRC contexts (the UE context isprovided by the previous serving eNB over the X2 interface) to resumesignalling and dedicated radio bearers (SRBs and DRBs) in the UE basedon its previously configured UE context. Modification to the SRBs, DRBs,measurement configuration and security configuration by the new-eNB,before resumption, is also possible by means of the reestablishmentprocedure.Because the RRC Connection Reestablishment procedure does not involveNAS level signalling and optionally security activation signalling overthe air, it is much lighter in terms of required signalling than aregular idle to connected mode transition. The other advantage is that aeNB on which the connection is being resumed can make use of theoptionality of various fields and hence minimize the size of the overthe air signalling for the measurement and radio resource configurationsduring the reestablishment procedure.With reference to FIG. 28, to extend this procedure for RRC connectionresumption the following enhancements need to be made.

-   -   1. At the time of RRC connection suspension, the serving eNB        either,        -   a. Stores a full back-up of the containers it has sent to            the MME along with the corresponding eNB and MME identities            associated to the UE at the time the suspension took place,            or        -   b. stores the eNB and MME identities of the UE, associate a            suspension status with them and forward the actual            containers along with the eNB and MME identities of the UE            to the MME.    -   2. The serving eNB can optionally prepare either some eNBs in        the vicinity (as it does for the case of X2-handover) or        possibly all the eNBs under the MME (or within the validity area        such as the Tracking Area (TA)) with the UE context and any        other information required for a connection reestablishment on        any one of those eNBs. The preparation is tagged with a        ‘suspension indicator’ flag to indicate to the target eNB that        the preparation is actually for a suspended RRC connection.    -   3. Optionally the X2 interface protocol may be enhanced such        that based on the old eNB credentials provided in the ‘RRC        connection reestablishment request’, the new-eNB will be able to        identity and query the old eNB for the UE context. If available        the Old eNB may provide the UE context to the new-eNB in a        similar manner as used during a X2 handover preparation.        Alternatively the Old eNB may be able to query the MME for the        UE context as it does during a TAU using the UE identities and        the suspension indicator. The new-eNB may indicate to the old        eNB that this is for a suspended RRC connection.

The details of possible actions in the reestablishment proceduresequence for the purposes of connection reactivation are as follows:

-   -   1. Initially the UE considers its suspended RRC connection to be        valid    -   2. The UE detects the need to resume the RRC connection either        due to the arrival of data pending uplink transmission or due to        reception of paging from the network.    -   3. On its current camped cell within the validity area, UE sends        an RRC connection reestablishment request with a new cause        indicating reactivate' or new IE to indicate the reactivation of        a suspended RRC Connection or context. It may include some or        all the details as per the regular reestablishment request        message structure (3GPP TS 36.331). The details of C-RNTI and        Source PhysicalCellIdentity shall be those that relate to the        cell/eNB on which the RRC connection was originally suspended.        Short MAC-I derivation is as per the usual procedure (refer to        section 5.3.7.4 of 3GPP TS 36.331) however using the parameters        relating to the cell/eNB on which the RRC connection was        originally suspended.    -   4. The new-eNB detects the reestablishment cause as ‘reactivate’        (or the RRC Connection Reestablishment request message includes        a new IE to request the reactivation of a suspended RRC        connection)        -   a. Either it has a stored UE context available (the new-eNB            102 b may be the same as the old eNB on which the connection            was originally suspended or may be one of the eNBs that have            been prepared by the old eNB 102 a) or        -   b. Based on the source cell details provided by the UE, the            new-eNB 102 b is able to retrieve the suspended UE context            from the old eNB 102 a over an X2 interface using a new or            modified message.    -   5. The old eNB 102 a has either the stored UE context available        or it is able to retrieve this context from the MME 103 b using        the stored UE identities (in the same way as it retrieves UE        context for S1 handovers).    -   6. The old eNB 102 a provides to the new eNB 102 b the UE        context (containers with AS-Config containing the suspended RRC        context and AS-Context containing the information to        re-establish the RRC connection on the new-eNB).    -   7. The new-eNB 102 b uses the received information to validate        the security context of the UE 101 and sends an RRC Connection        Reestablishment message to the UE for SRB1 resumption and new        security key derivation.    -   8. The UE resumes SRB1, derives new security keys and sends an        RRC Connection Reestablishment Complete message to the new-eNB.    -   9. The new-eNB 102 b sets up the UE session with the MME 103 b        following the S1 path switch as it would do in case of a regular        RRC connection reestablishment.        -   a. The MME 103 b in turn creates a user plane session for            the UE with the S-GW 103 a if the S1-U was deleted earlier            or        -   b. The MME facilitates a regular S1 path switch if the S1-U            was kept active between the S-GW and the old-eNB on which            the connection was originally suspended        -   c. The MME may facilitate a S1 path switch but with an            additional reactivate indicator to the S-GW if the S1-U was            suspended at the time of suspension    -   10. The new-eNB sets up SRB2 and DRB configurations and        measurement configuration and sends an RRC Connection        Reconfiguration message to the UE.    -   11. The UE applies the received configuration, reactivates SRB2        and DRB, and transmits an RRC Connection Reconfiguration        Complete to the eNB. Thereafter the UE may proceed with any user        plane date transfer as usual.

As an alternative to reuse of the reestablishment procedure forreactivation of a suspended connection, an equivalent procedure may beemployed but which uses different messages or message definitions Forexample, a new RACH message3 and message 4 (see 3GPP TS 36.331) may bedefined for the purposes of RRC connection reactivation request and RRCconnection reactivation respectively and which could follow the sameprinciples as those of reestablishment.

A further alternative option could be to resort to the regular RRCConnection

Establishment procedure within the validity area too, thereby followingthe reactivation procedure described below (Example Scenario 12) in thevalidity area change case.

Example Scenario 11

FIG. 29 shows a message sequence chart describing the details ofpossible actions if the reestablishment procedure fails during theconnection reactivation. The steps of FIG. 29 include:

-   -   1. Initially the UE 101 has a suspended RRC connection        associated with a cell under the control of old eNB 102 a.    -   2. The UE detects the need to reactivate the RRC connection        either due to the arrival of data pending uplink transmission or        due to reception of paging from the network.    -   3. The UE 101 is camped on a cell under the control of new eNB        102 b and which lies within the validity area. The UE sends an        RRC connection reestablishment request with a new cause        indicating ‘reactivate’ or a new IE to indicate the reactivation        of a suspended RRC Connection or context towards a new eNB 102        b. It may include some or all of the details that would be        included within a regular reestablishment request message        structure. The details of C-RNTI and Source PhysicalCellIdentity        shall be those that relate to the cell/eNB 102 a on which the        RRC connection originally was suspended. Short MAC-I derivation        is as per the usual procedure. However using the parameters        relating to the cell/eNB 102 a on which the RRC connection        originally was suspended.    -   4. The new-eNB 102 b either fails to resolve the UE identity to        retrieve the prepared context or fails to uniquely identity the        source eNB from which the UE context has to be retrieved.    -   5. The new-eNB 102 b rejects the reestablishment request.    -   6. The UE 101 applies the default configuration for SRB0 whilst        retaining the rest of the suspended UE context and starts a RRC        connection establishment procedure.    -   7. The UE 101 transmits a RRC connection request message        optionally identifying the setup cause as resume.    -   8. The new-eNB 102 b sets up SRB1 for the UE and transmits RRC        connection setup message to the UE.    -   9. The UE configures SRB1 and transmits a RRC connection setup        complete message including an initial NAS message, for example:        Service Request. UE also includes the UE identifiers and MME        identifiers related allocated when the RRC connection got        suspended.    -   10. The new-eNB 102 b requests the designated MME 103 b to setup        a S1 context for the UE.    -   11. From the context request, MME 103 b knows that it has stored        containers pertaining to the suspended RRC context for this UE        and retrieves the same.    -   12. MME 103 b switches the S1 path from the old eNB 102 a on        which the connection was originally suspended to the new-eNB 102        b.    -   13. If the S1 path switch is not possible, the S1 connection is        released with old eNB 102 a and is setup with the new-eNB 102 b.    -   14. The MME 103 b forwards the security context for the UE and        the stored containers related to the suspended RRC connection.    -   15. The New-eNB 102 b can now derive a delta configuration that        needs to be signalled to the UE by comparing the known current        configuration at the UE with the configuration desired by the        new eNB 102 b. Alternatively, new eNB 102 b may also instruct        the UE to throw away the suspended configuration and adopt a new        configuration by setting the ‘full config’ IE.    -   16. The New eNB 102 b transmits a security mode command to the        UE and RRC connection reconfiguration message to the UE which        will lead to the reactivation of SRB2 and other DRBs at the UE.

Example Scenario 12

Reactivation at a change in validity area boundary is based on the TAUprocedure outlined above in the mobility procedures. The RRC connectionrequired for performing the TAU procedure may be established following anormal RRC connection establishment approach.The advantages of a regular RRC connection establishment procedure arethat this allows:

-   -   a. NAS and AS security to anyway be activated based on the base        key of the new MME    -   b. Bearer mappings and channel configurations to be modified as        suited for the new MME/new-eNB    -   c. Measurement contexts to be refreshed with the neighbour cell        configurations suited for the new MME/new-eNB.        Thus this approach of reactivating the connection during a TAU        procedure comprises:    -   a. Invalidating the suspended RRC connection and    -   b. Setting up a new RRC connection (with full new-config or        differential new config) via the TAU    -   c. Retaining/suspending/releasing the new connection as desired        once ongoing data transfer and signalling is considered complete        The details of this approach are described above as part of the        mobility procedures.        However, if establishment of a new RRC connection is deemed to        be inefficient at TA boundaries (for example when UEs move        between the TAs), the RRC connection reestablishment procedure        may need to be modified to incorporate NAS signalling between        SRB1 reactivation and SRB2/DRB reactivation. This procedure is        similar to the reestablishment procedure described in scenario        11 above except that in this case the new-eNB is connected to an        MME different to that to which the old-eNB is connected.        Therefore during the initial reestablishment, the new-eNB will        retrieve the UE RRC context from the old eNB via the X2        interface if available or from the old-MME via the new MME. New        signalling messages to retrieve this context will be required        between the MMEs and between the eNB and MME. Once the security        activation and SRB1 reactivation phase of the reestablishment        procedure is successful, regular TAU signalling can take place        over the resumed SRB1. The TAU signalling can be used to        reactivate/release/suspend the RRC connection at the end of the        TAU in the same way as described above.

Example Scenario 13

There are numerous possible embodiments of the RRC suspend concept. Inthis scenario, an embodiment is described in which the objective is tomaximise compatibility with existing system procedures and signallingmessages, and thereby to minimise the specification work necessary tointegrate the scheme within 3GPP LTE specifications.

The embodiment is based upon the following guiding principles:

-   -   Procedures for reactivation of a suspended RRC context are        largely based on existing procedures for RRC re-establishment        (and which are currently used for recovery from Radio Link        Failure    -   The S1 connection is not suspended during a Uu suspension. This        avoids the need for signalling between the Radio Access Network        and the Core Network each time a Uu connection is suspended or        resumed (i.e. from the CN point of view, the UE remains in        connected mode).    -   The UE always informs the RAN in the event that it reselects        another cell whilst suspended. This avoids the need for paging        escalation (via other eNBs, or via a wide area spanning multiple        cells/eNBs) in the event that downlink data arrives at the eNB        of the suspension cell, but the UE has since moved to another        cell without notifying the network. There are two potential        variants concerning this cell location notification:        -   i) The first alternative is for the UE to move to idle and            to send a TAU via the new cell following a reselection. On            receipt of the TAU, the MME is made aware that the UE is now            idle and can initiate the release of the S1 to the old cell.            If new data arrives for the UE beyond this point, a new RRC            connection (and S1 connection) will be established            (following network paging of the UE in the case of DL data            arrival)        -   ii) The second alternative is for the UE to send a            re-establishment request in the new cell following a            reselection. The eNB of the new cell may then decide to            perform operations similar to those used during handover in            order to prevent the UE from moving back to full idle mode.            If the eNB of the new cell is the same as that of the old            cell, the UE context information is readily available within            the eNB, hence the eNB can complete the re-establishment            procedure with the UE without contacting other network            nodes. If the eNB of the new cell is different to that of            the old cell, the new eNB may attempt to fetch the UE            context from the old eNB using existing X2 ‘forward            handover’ procedures (“RLF indication message” of 3GPP TS            36.423) introduced in 3GPP Release 9 for RLF recovery and            the new eNB can complete the re-establishment procedure with            the UE and can initiate an S1 path switch request to the MME            per the normal handover procedure.    -   If re-establishment procedures fail (either when accessing the        suspension cell or a new cell), or if they are rejected by the        network, the UE resorts to NAS-based RLF recovery as per        existing procedures, and hence returns to idle and sends a TAU        via the currently camped cell. This will result in the        establishment of a new RRC connection.

In order to implement the above embodiment, the following changes arerequired to the specifications:

-   -   1) A new “Suspend Request” message may be defined for uplink        communications, thereby allowing the UE to request or initiate a        suspension of the RRC connection. If suspension is purely        network-triggered (without UE input to the decision), definition        of this message is not required. The message may be a new RRC        message, or may comprise a modification to an existing RRC        message. The message may alternatively be conveyed at a MAC        layer for example within a MAC control element (CE).    -   2) A “Suspend Command” message may be defined for downlink        communications in order to allow the network to command a        suspension of the UEs present RRC connection. In order to        provide this functionality, an existing message (such as RRC        release, or RRC reconfiguration) may be modified, or a new        message may be defined. Alternatively the message may be        conveyed at a MAC layer for example within a MAC CE.    -   3) New triggers for initiating RRC re-establishment are defined.        When the UE's RRC connection is currently suspended, these        include one or more of:        -   a. Reception of a paging message from the network (for            network-originated-DL-data)        -   b. The arrival of new mobile-originated (UL) data at the UE        -   c. Following the UE's reselection to any other cell

FIG. 30 is a message sequence chart showing an over view of the abovesteps for RRC Connection Suspension followed by RRC ConnectionRe-establishment between a UE 101 and a EUTRAN 102.

-   -   1. Initially the UE 101 has an active (non-suspended) RRC        connection with EUTRAN 102.    -   2. A trigger is generated at either the UE 101 or the EUTRAN 102        indicating that it would be preferable to suspend the RRC        connection. This trigger may be generated by a suspension        criterion or criteria being met at the UE or the EUTRAN, as        discussed in the above examples.    -   3a. If the trigger is generated at the UE, the UE sends a        connection suspend request message. In this example, the UE uses        a new message (e.g. an RRC Connection Suspend Request message)        to the EUTRAN. Other new or existing 3GPP messages could also be        used for this purpose. If the trigger is generated at the EUTRAN        the connection suspend request message is not sent by the EU and        this step is omitted.    -   3b. On receipt of the RRC Connection Suspend Request message by        the EUTRAN or the if the trigger is generated at the EUTRAN, the        EUTRAN sends a connection suspend command message to the UE. In        this example, the EUTRAN uses a new message (e.g. a RRC        Connection Suspend command message) to the UE. In another        example, the EUTRAN could use a modified form of an RRC        Connection Reconfiguration message or a modified form of an RRC        Release message as a connection suspend command message. In        these cases the modified RRC Connection Reconfiguration message        or modified RRC Release message would be modified so that the        effect at the UE would be for the RRC connection to be suspended        rather than reconfigured or released. This modification could        for example include a new information element (IE) to indicate        that the purpose is to suspend the RRC connection. For example,        this new IE may be labelled ‘Suspend RRC Connection’, ‘Suspend        Command’, ‘Suspension Command’, ‘Suspend Indicator’, ‘Suspension        Indicator’ or something different. The new IE may be optionally        present in the message and the presence of the IE in the message        may cause the UE to suspend the RRC connection. Alternatively        the new IE may be a Boolean value and the setting of the IE to        TRUE may cause the UE to suspend the RRC connection. Other new        or existing 3GPP messages could also be used for this purpose.    -   3c. Optionally, the UE may then send a RRC(L3) acknowledgement        or a MAC(L2) acknowledgement to the EUTRAN    -   4. The RRC connection is then suspended with at least the        security context being stored at the UE and/or the EUTRAN.    -   5. After the RRC connection has been suspended, paging reception        and mobility procedures at the UE are similar to the procedures        adopted by the UE when the UE is in idle mode (the UE monitors        downlink signals for paging messages and performs UE-based        mobility procedures (e.g. cell reselection)).    -   6. To re-establish a suspended RRC connection a trigger to        resume from suspend is generated at the UE or the EUTRAN.        Typically, the trigger is generated at the UE and may be one        of (i) reception of a paging message from the EUTRAN for        network-originating downlink data for the UE; (ii) the        generation at the UE of new mobile-originated uplink data;        or (iii) following the UE's reselection to another cell. Other        triggers as described above are possible as well.    -   7. On generation of the trigger, the UE sends a connection        re-establishment request message. In this example, the UE sends        a RRC Connection Reestablishment Request message with a RRC        Suspended Indication to the EUTRAN. The RRC Suspended Indication        may be contained within a reestablishment cause field of the RRC        Connection Reestablishment Request message.    -   8. The EUTRAN then responds with a connection re-establishment        command message. In this example, the EUTRAN sends a RRC        Connection Reestablishment command message to the UE.    -   9. When the RRC connection has been re-established, the UE sends        a connection re-establishment complete message to confirm the        RRC connection has been re-established. If a RRC Connection        Reestablishment command message is used as the connection        re-establishment command message, the UE sends a RRC Connection        Reestablishment Complete message to the EUTRAN.    -   Optionally (and possibly as an alternative to using a RRC        Connection Reestablishment command message shown in step 8        above), the EUTRAN may also respond with a RRC Connection        Reconfiguration message. In a scenario where, the EUTRAN would        use the RRC Connection Reconfiguration message instead of a RRC        Connection Reestablishment command message as the connection        reestablishment command message. In that example, the EUTRAN        could use a modified form of the RRC Connection Reconfiguration        so that the effect at the UE would be for the RRC connection to        be re-established. This modification could for example include a        new information element (IE) to indicate that the purpose is to        re-establish the RRC connection. For example, this new IE may be        labelled ‘Suspended RRC Connection’, ‘Suspend Indicator’,        ‘Suspension Indicator’ or something different. The new IE may be        optionally present in the message and the presence of the IE in        the message may cause the UE to re-establish the RRC connection.        Alternatively the new IE may be a Boolean value and the setting        of the IE to TRUE may cause the UE to suspend the RRC        connection. Other new or existing 3GPP messages could also be        used for this purpose.    -   11. If a RRC Connection Reconfiguration message is received at        the UE, the UE then responds to that message with a RRC        Connection Reconfiguration Complete message. The UE would use        the RRC Connection Reconfiguration Complete message as a        connection reestablishment complete message. Other new or        existing 3GGPP messages could also be used for this purpose.    -   12. At this point, the RRC connection is fully re-established        and user plane data communication with the UE may be initiated        or resumed.

The example scenarios 14 to 16 below and the respective FIGS. 31 to 33give more detailed examples of specific scenarios within the generalscenario discussed above in scenario 13 and shown in FIG. 30.

Example Scenario 14

FIG. 31 shows a message sequence chart for re-establishment of a UE 101from suspend on an eNB 102 a that has the RRC connection information orcontext for the UE 101. The eNB 102 a may be the eNB that suspended theRRC connection or it could be a different eNB.

-   -   1. When a trigger is generated at the UE 101 for        re-establishment of a suspended RRC connection, the UE sends a        RRC Connection Reestablishment Request message to the eNB 102 a.        The Reestablishment Request message may contain a        reestablishment cause field allowing the UE 101 to indicate to        eNB 102 a that the reason for the reestablishment is to        reactivate a previously-suspended RRC connection.    -   2. When the eNB 102 a receives the request message, the eNB 102        a retrieves the stored RRC connection information for UE 101 and        sends a RRC Connection Reestablishment command message to the UE        101.    -   3. The UE performs re-establishment of the suspended RRC        connection and sends a RRC Connection Reestablishment Complete        message to the eNB.    -   4. The eNB then sends a RRC Connection Reconfiguration message        to the UE.    -   5. The UE completes the RRC connection reconfiguration and sends        an RRC Connection Reconfiguration Complete message to the eNB to        complete the re-establishment of the RRC connection.

Example Scenario 15

FIG. 32 shows a message sequence chart for re-establishment of asuspended RRC connection for a UE 101 that is camped on an eNB 102 bthat does not have the RRC connection information or context.

-   -   1. When a trigger is generated at the UE 101 for        re-establishment of a suspended RRC connection, the UE sends a        RRC Connection Reestablishment Request message to the eNB 102 b.        The Reestablishment Request message may contain a        reestablishment cause field allowing the UE 101 to indicate to        eNB 102 b that the reason for the reestablishment is to        reactivate a previously-suspended RRC connection. The        Reestablishment Request message may also contain information        enabling eNB 102 b to identify the eNB (eNB1 102 a) that        originally suspended the UE's RRC connection.    -   2. eNB 102 b does not have the RRC connection information for UE        101 and so sends a RLF Indication message (context fetch) to the        old eNB 102 a that suspended the RRC connection.    -   3. The old eNB responds by sending a handover request to the new        eNB 102 b including the RRC connection information for the UE        101.    -   4. The new eNB 102 b responds with a handover request        acknowledgement to the old eNB.    -   5. The new eNB 102 b then sends a RRC Connection Reestablishment        message to the UE 101.    -   6. The UE 101 performs re-establishment of the suspended RRC        connection and responds with an RRC Connection Reestablishment        Complete message to the new eNB 102 b.    -   7. The new eNB then sends an RRC Connection Reconfiguration        message to the UE.    -   8. The UE completes the RRC connection reconfiguration and sends        an RRC Connection Reconfiguration Complete message to the new        eNB to complete the re-establishment of the RRC connection.    -   9. The new eNB 102 b then completes an S1 path switch with MME        103 b.    -   10. The MME 103 b sends the new eNB a handover request        acknowledgement.    -   11. The new eNB 102 b then sends a message to the old eNB 102 a        to cause the old eNB 102 a to release the RRC connection        configuration or context for the UE 102.

Example Scenario 16

FIG. 33 shows a message sequence chart for failure of re-establishmentfrom suspend for a UE 101 followed by a NAS recovery procedure usingTracking Area Update (TAU).

-   -   1. When a trigger is generated at the UE 101 for        re-establishment of a suspended RRC connection, the UE sends an        RRC Connection Reestablishment Request message to the eNB 102 a.    -   2. When the eNB 102 a receives the request message, the eNB 102        a determines that it does not have the RRC connection        information for UE 101 and decides to reject the request for        re-establishment. The eNB 102 a then sends a RRC Connection        Reject command message to the UE 101.    -   3. The UE then sends a RRC Connection Request message to the eNB        for a new RRC connection with the eNB.    -   4. The eNB 102 a then sends an RRC Connection Setup message to        the UE 101.    -   5. The UE completes the RRC connection setup and sends a RRC        Connection Setup Complete message to the eNB 102 a.    -   6. eNB 102 a then sends a DL Information Transfer message to the        UE.    -   7. This is followed by the eNB 102 a sending a RRC connection        release message to the UE 101.

Additional aspects of the present disclosure relating to the operationof a UE to suspend an RRC connection will now be set out in thefollowing numbered clauses.

1. A method, implemented in a user equipment (UE) for use with a RadioAccess Network (RAN), comprising:

the UE suspending an established RRC connection with the RAN;

the UE monitoring, whilst the RRC connection is suspended, for at leastone of: paging and notifications of downlink data for the UE; and

the UE storing RRC connection data related to the suspended RRCconnection, said RRC connection data being usable by the UE toreactivate the suspended RRC connection.

2. A method as set out in clause 1, wherein RRC connection datacomprises data representing one or more of:

-   -   the configuration of radio bearers in the established RRC        connection;    -   security parameters relating to the established RRC connection;    -   temporary cell identifiers;    -   MAC configuration;    -   Physical Layer configuration.        3. A method as set out in clause 1 or 2, further comprising        marking the stored RRC connection data to indicate the        suspension of the RRC connection.        4. A method as set out in clause 1, 2 or 3, wherein the UE        suspends the established RRC connection in response to an RRC        connection suspension criterion being met.        5. A method as set out in clause 4, the RRC connection        suspension criteria comprising one or more of:    -   the expiry of a timer at the UE;    -   reception of a message at the UE.        6. A method as set out in any preceding clause, wherein the RAN        has an established user plane connection with a Core Network        (CN) for the UE, the method further comprising maintaining the        established user plane connection between the RAN and the CN        while the RRC Connection is suspended.        7. A method as set out in clause 6, wherein when the RAN node        for which the suspended RRC connection is valid receives from        the CN downlink data for the UE, the RAN node buffers the        downlink data and pages the UE a transmits a notification of        downlink data for the UE.        8. A method as set out in clause 7, wherein, in response to the        RAN node receiving no response from the UE to the paging or to        the notification of downlink data, the RAN node sends to the CN        a paging escalation message.        9. A method as set out in any of clauses 1-5, further comprising        the UE or a RAN node sending a message to inform any node in the        Core Network (CN) that the RRC connection is suspended.        10. A method as set out in clause 9, wherein the RAN has an        established user plane connection with the CN for the UE, the        method further comprising suspending the established user plane        connection between the CN and the RAN.        11. A method as set out in clause 10, wherein the message sent        to the CN includes an identification of the UE, the method of        suspending the established user plane connection between the CN        and the RAN comprising the RAN or one or more nodes in the CN or        both:

discontinuing transmission and reception of user plane data for the UEover the established user plane connection between the RAN and the CN;and

storing CN-RAN connection data representing the established user planeconnection, said CN-RAN connection data being usable to later resumetransmission and reception of user plane data to the UE by reactivatingsaid user plane connection between the RAN and the CN as the result ofan RRC connection reactivation process.

12. A method as set out in clauses 10 or 11, wherein when downlink datafor the UE is received at the CN, a node of the CN buffers the downlinkdata and the CN initiates the paging of the UE by one or more cells ofthe RAN.13. A method as set out in clauses 10, 11 or 12, further comprising anode of the CN maintaining a validity indicator for the UE, saidvalidity indicator being usable in checking the validity of the said RRCconnection as part of the RRC connection reactivation process.14. A method as set out in clause 13, wherein the value of the validityindicator is dependent on one or more of: the location of the UE; atimer.15. A method as set out in any preceding clauses, further comprising:

the UE performing autonomous mobility control by cell selection orreselection processes during the time that the RRC connection issuspended and the UE relinquishing mobility control to the RAN as aresult of the reactivation of the suspended RRC connection or a normalRRC connection process to establish a new RRC connection with the UE.

16. A method as set out in clause 15, wherein when the UE selects a cellof the RAN in which the suspended RRC Connection represented by thestored RRC connection data is invalid, the UE continues to store the RRCconnection data and omits to perform any communication with the CN toinform the CN of the mobility of the UE.17. A method as set out in clause 15, wherein when the UE selects a cellof the RAN in which the suspended RRC Connection represented by thestored RRC connection data is invalid, the UE transmits a messageinforming the RAN or the CN of this event.18. A method as set out in clause 17, wherein the UE also releases theRRC connection and enters idle mode as the result of selecting a cell ofthe RAN in which the suspended RRC Connection represented by the storedRRC connection data is invalid.19. A method as set out in clause 17 or 18, wherein receipt by the RANor the CN of the message sent by the UE causes the RAN or CN to performone or more of: release the invalid RRC Connection; initiate a normalRRC connection process to establish a new RRC connection with the UE;release an established user plane connection for the UE between the CNand RAN.20. A method as set out in clause 15, wherein when the UE selects a cellof the RAN in which the suspended RRC Connection represented by thestored RRC connection data is invalid, the UE continues to store the RRCconnection data and transmits a message informing the RAN or the CN ofthis event.21. A method as set out in any preceding clause, further comprising:

the UE determining whether or not the suspended RRC connection is stillvalid by reference to the stored RRC connection data; and

in response to the UE determining that the suspended RRC connection isstill valid, the UE sending an RRC connection reactivation requestmessage to the RAN.

22. A method as set out in clause 21, further comprising:

in response to receiving an RRC connection reactivation complete messagefrom the RAN, the UE resuming user plane data transfer with the RAN overthe reactivated RRC connection.

23. A method as set out in clause 22, further comprising:

in response to receiving an RRC connection reactivation reject messagefrom the RAN, the UE releasing the suspended RRC connection and enteringidle mode; and

the UE thereafter initiating a normal RRC connection establishmentprocess to establish a new RRC connection with the RAN.

24. A method of clause 23, wherein a RAN node transmits the RRCconnection reactivation reject message to the UE in response to the RANnode determining that it does not have a valid suspended RRC connectionfor the UE.25. A method as set out in any preceding clause, further comprising:

the UE determining whether or not the suspended RRC connection is stillvalid by reference to the stored RRC connection data;

in response to the UE determining that the suspended RRC connection isinvalid, the UE releasing the suspended RRC connection and entering idlemode; and

the UE thereafter initiating a normal RRC connection establishmentprocess to establish a new RRC connection with the RAN.

26. A method of any of clauses 21 to 25, wherein the UE determiningwhether or not the suspended RRC connection is still valid comprises atleast one of:

-   -   determining whether the UE is currently in a cell of the RAN in        which the suspended RRC Connection represented by the stored RRC        connection data is still valid; and    -   determining whether a timer has not expired.        27. A method of clauses 21-26, further comprising the UE        relinquishing mobility control of the UE to the RAN as a result        of the reactivation of the suspended RRC connection or the        establishment of a new RRC connection.        28. A method of any preceding clause, further comprising        initiating the reactivation of the suspended RRC connection in        response to:    -   the UE generating uplink data via the user plane of an RRC        connection; or    -   reception at the UE paging; or    -   reception at the UE of a notification that the RAN or the CN has        downlink data buffered to send to the UE.        29. A method as set out in any preceding clause, wherein the UE        is configured to communicate with the RAN in accordance with the        LTE or LTE Advanced protocols.        30. A method as set out in any preceding clause, wherein the RAN        is configured to communicate with the UE in accordance with the        LTE or LTE Advanced protocols.        31. A method as set out in any preceding clause, wherein the RAN        node or nodes is/are eNode B(s).        32. A User Equipment (UE) for use with a Radio Access Network        (RAN), the UE being configured to:

suspend an established RRC connection with the RAN;

monitor, whilst the RRC connection is suspended, for at least one of:pagingand notifications of downlink data for the UE; and

store RRC connection data representing the suspended RRC connection,said RRC connection data being usable by the UE to reactivate thesuspended RRC connection.

33. A UE as set out in clause 32, wherein RRC connection data comprisesdata representing one or more of:

-   -   the configuration of radio bearers in the established RRC        connection;    -   security parameters relating to the established RRC connection;    -   temporary cell identifiers;    -   MAC configuration;    -   Physical Layer configuration.        34. A UE as set out in clause 32 or 33, further comprising the        UE being configured to mark the stored RRC connection data to        indicate the suspension of the RRC connection.        35. A UE as set out in clause 32, 33 or 34, further comprising        the UE being configured to suspend the established RRC        connection in response to an RRC connection suspension criterion        being met.        36. A UE as set out in clause 35, wherein the RRC connection        suspension criteria comprise one or more of:    -   the expiry of a timer at the UE;    -   reception of a message at the UE.        37. A UE as set out in any of clauses 32-36, further comprising:

the UE being configured to perform autonomous mobility control by cellselection or reselection processes during the time that the RRCconnection is suspended and the UE relinquishing mobility control to theRAN as a result of an the reactivation of the suspended RRC connectionor a normal RRC connection process to establish a new RRC connectionwith the UE.

38. A UE as set out in clause 37, the UE being configured such that,when the UE selects a cell of the RAN in which the suspended RRCConnection represented by the stored RRC connection data is invalid, theUE continues to store the RRC connection data and omits to perform anycommunication with the CN to inform the CN of the mobility of the UE.39. A UE as set out in clause 37, the UE being configured such that,when the UE selects a cell of the RAN in which the suspended RRCConnection represented by the stored RRC connection data is invalid, theUE transmits a message informing the RAN or the CN of this event.40. A UE as set out in clause 39, the UE being configured such that theUE also releases the RRC connection and enters idle mode as the resultof selecting a cell of the RAN in which the suspended RRC Connectionrepresented by the stored RRC connection data is invalid.41. A UE as set out in clause 39 or 40, wherein receipt by the RAN orthe CN of the message sent by the UE causes the RAN or CN to perform oneor more of: releasing the invalid RRC Connection; initiating a normalRRC connection process to establish a new RRC connection with the UE;releasing an established user plane connection for the UE between the CNand RAN.42. A UE as set out in clause 37, the UE being configure such that, whenthe UE selects a cell of the RAN in which the suspended RRC Connectionrepresented by the stored RRC connection data is invalid, the UEcontinues to store the RRC connection data and transmits a messageinforming the RAN or the CN of this event.43. A UE as set out in any of clauses 32-42, further comprising the UEbeing configured such that, as part of the RRC connection reactivationprocess:

the UE determines whether or not the suspended RRC connection is stillvalid by reference to the stored RRC connection data; and

in response to the UE determining that the suspended RRC connection isstill valid, the UE sends an RRC connection reactivation request messageto the RAN.

44. A UE as set out in clause 43, further comprising:

the UE being configured such that, in response to receiving an RRCconnection reactivation complete message from the RAN, the UE resumesuser plane data transfer with the RAN over the reactivated RRCconnection.

45. A UE as set out in clause 43, further comprising:

the UE being configured such that, in response to receiving an RRCconnection reactivation reject message from the RAN, the UE releases thesuspended RRC connection and entering idle mode; and

the UE configured to thereafter initiate a normal RRC connectionestablishment process to establish a new RRC connection with the RAN.

46. A UE as set out in clause 43, wherein a RAN node transmits the RRCconnection reactivation reject message to the UE in response to the RANnode determining that it does not have a valid suspended RRC connectionfor the UE.47. A UE as set out in any of clauses 32-46, further comprising the UEbeing configured to:

determine whether or not the suspended RRC connection is still valid byreference to the stored RRC connection data;

in response to the UE determining that the suspended RRC connection isinvalid, release the suspended RRC connection and enters idle mode; and

thereafter initiate a normal RRC connection establishment process toestablish a new RRC connection with the RAN.

48. A UE as set out in any of clauses 43-47, further comprising the UEbeing configured to, as part of determining whether or not the suspendedRRC connection is still valid, determine at least one of:

-   -   whether the UE is currently in a cell of the RAN in which the        suspended RRC Connection represented by the stored RRC        connection data is still valid; and    -   whether a timer has not expired.        49. A UE as set out in any of clauses 43-48, further comprising        the UE being configured to relinquish mobility control of the UE        to the RAN as a result of the reactivation of the suspended RRC        connection or the establishment of a new RRC connection.        50. A UE as set out in any of clauses 32-49, further comprising        the UE being configured to initiate the reactivation of the        suspended RRC connection reactivation process in response to at        least one of:    -   the UE generating uplink data via the user plane of an RRC        connection;    -   reception at the UE of paging; and    -   reception at the UE of a message indicating that the RAN or the        CN has downlink data buffered to send to the UE over the user        plane of an RRC connection.        51. A UE as set out in any of clauses 32-50, wherein the UE is        configured to communicate with the RAN in accordance with the        LTE or LTE Advanced protocols.        52. A wireless communications system comprising a UE as set out        in any of clauses 32-51, and a RAN having an established user        plane connection with a Core Network (CN) for the UE, the system        being configured to maintain the established user plane        connection between the RAN and the CN while the RRC Connection        is suspended.        53. A wireless communications system as set out in clause 52,        further comprising the RAN node for which the suspended RRC        connection is valid being configured such that when the RAN node        receives from the CN downlink data for the UE, the RAN node        buffers the downlink data and pages the UE or transmits a        notification of downlink data for the UE.        54. A wireless communications system as set out in clause 53,        further comprising the RAN node being configured such that, in        response to the RAN node receiving no response from the UE to        the paging or to the notification of downlink data, the RAN node        sends to the CN a paging escalation message.        55. A wireless communications system comprising a UE as set out        in any of clauses 32-51, and a RAN, the wireless communications        system being configured such that the UE or a RAN node sends a        message to inform any node in the Core Network (CN) that the RRC        connection is suspended.        56. A wireless communications system as set out in clause 55,        wherein the RAN has an established user plane connection with        the CN for the UE, the wireless communications system being        configured such that the wireless communications system suspends        the established user plane connection between the CN and the        RAN.        57. A wireless communications system as set out in clause 56,        further comprising the wireless communications system being        configured such that the message sent to the CN includes an        identification of the UE, and such that, to suspend the        established user plane connection between the CN and the RAN,        the RAN or one or more nodes in the CN or both:

discontinue transmission and reception of user plane data for the UEover the user plane connection between the RAN and the CN; and

store CN-RAN connection data representing the established user planeconnection, said CN-RAN connection data being usable to later resumetransmission and reception of user plane data to the UE by resuming saiduser plane connection between the RAN and the CN as the result of an RRCconnection reactivation process.

58. A wireless communications system as set out in clauses 56 or 57,further comprising the wireless communications system being configuredsuch that, when downlink data for the UE is received at the CN, a nodeof the CN buffers the downlink data and the CN initiates the paging ofthe UE by one or more cells of the RAN.59. A wireless communications system as set out in clauses 56, 57 or 58,further comprising the wireless communications system being configuredsuch that a node of the CN maintains a validity indicator for the UE,said validity indicator being usable in checking the validity of thesaid RRC connection as part of the RRC connection reactivation process.60. A wireless communications system as set out in clause 59, whereinthe value of the validity indicator is dependent on one or more of: thelocation of the UE; a timer.61. A wireless communications system as set out in any of clauses 52-60,wherein the RAN is configured to communicate with the UE in accordancewith the LTE or LTE Advanced protocols.62. A wireless communications system as set out in any of clauses 52-60,wherein the RAN node or nodes is/are eNode B(s).63. A computer program product having instructions which when carriedout by a processor of User Equipment (UE) for use with a Radio AccessNetwork (RAN) cause the UE to be configured to operate in accordancewith a method as set out in any of clauses 1-31.64. A computer program product having instructions which when carriedout by a processor of a node of a Radio Access Network (RAN) for usewith a user equipment (UE) cause the RAN node to be configured tooperate in accordance with a method as set out in any of clauses 1-31.

Additional aspects of the present disclosure relating to the operationof a RAN node to suspend an RRC connection will now be set out in thefollowing numbered clauses.

1. A method, implemented in a node of a Radio Access Network (RAN) foruse with a user equipment (UE), comprising:

the RAN node suspending an established RRC connection with the UE;

the RAN node thereafter being operable, whilst the RRC connection issuspended, to page the UE paging or transmit notification of downlinkdata for the UE or both; and

the RAN node storing RRC connection data related to the suspended RRCconnection, said RRC connection data being usable by the RAN node toreactivate the suspended RRC connection.

2. A method as set out in clause 1, wherein RRC connection datacomprises data representing one or more of:

-   -   the configuration of radio bearers in the established RRC        connection;    -   security parameters relating to the established RRC connection;    -   temporary cell identifiers;    -   MAC configuration;    -   Physical Layer configuration.

3. A method as set out in clause 1 or 2, further comprising marking thestored RRC connection data to indicate the suspension of the RRCconnection.

4. A method as set out in clause 1, 2 or 3, wherein the RAN nodesuspends the established RRC connection in response to an RRC connectionsuspension criterion being met.

5. A method as set out in clause 4, the RRC connection suspensioncriteria comprising one or more of:

-   -   the expiry of a timer at the RAN Node;    -   transmission of a message by the RAN node to the UE to instruct        suspension of the established RRC connection.

6. A method as set out in any of clauses 1-5, wherein the RAN node hasan established user plane connection with a Core Network (CN) for theUE, the method further comprising maintaining the established user planeconnection between the RAN node and the CN while the RRC Connection issuspended.

7. A method as set out in clause 6, wherein when the RAN node receivesfrom the CN downlink data for the UE, the RAN node buffers the downlinkdata and pages the UE a or transmits a notification of downlink data forthe UE.

8. A method as set out in clause 7, wherein, in response to the RAN nodereceiving no response from the UE to the paging or to the notificationof downlink data, the RAN node sends to the CN a paging escalationmessage.

9. A method as set out in any of clauses 1-5, further comprising the UEor the RAN node sending a message to inform any node in the Core Network(CN) that the RRC connection is suspended.

10. A method as set out in clause 9, wherein the RAN node has anestablished user plane connection with a CN for the UE, the methodfurther comprising suspending the established user plane connectionbetween the CN and the RAN for the UE.

11. A method as set out in clause 10, wherein the message sent to the CNincludes an identification of the UE, the method further comprising theRAN node or one or more CN nodes or both:

discontinuing transmission and reception of user plane data for the UEover the established user plane connection between the CN and the RANnode; and

storing CN-RAN connection data representing the established user planeconnection with the CN, said CN-RAN connection data being usable tolater resume transmission and reception of user plane data to the UE byreactivating said user plane connection between the CN and the RAN nodeas the result of an RRC connection reactivation process.

12. A method as set out in clauses 10 or 11, wherein when downlink datafor the UE is received at the CN, a node of the CN buffers the downlinkdata and the CN initiates the paging of the UE by one or more cells ofthe RAN.

13. A method as set out in clauses 10, 11 or 12, further comprising anode of the CN maintaining a validity indicator for the UE, saidvalidity indicator being usable in checking the validity of the said RRCconnection as part of the RRC connection reactivation process.

14. A method as set out in clause 13, wherein the value of the validityindicator is dependent on one or more of: the location of the user; atimer.

15. A method as set out in any preceding clause, further comprising: theRAN relinquishing to the UE, mobility control of the UE until the RANresumes mobility control of the UE as the result of the reactivation ofthe suspended RRC connection or a normal RRC connection process toestablish a new RRC connection with the UE.

16. A method as set out in clause 15, wherein when the UE selects a cellof the RAN in which the suspended RRC Connection represented by thestored RRC connection data is invalid, the RAN receiving a messageinforming the RAN of this event.

17. A method as set out in clause 16, wherein receipt by the RAN of themessage sent by the UE causes the RAN to perform one or more of: releasethe invalid suspended RRC Connection; initiate a new RRC connection withthe UE; release an established user plane connection for the UE betweenthe CN and RAN.

18. A method as set out in clause 15, 16 or 17, further comprising theRAN resuming mobility control of the UE as a result of reactivation ofthe suspended RRC connection or a normal RRC connection process toestablish a new RRC connection with the UE.

19. A method as set out in any preceding clause, wherein the RAN node,in response to receiving an RRC connection reactivation request messagefrom the UE:

determining whether or not the suspended RRC connection is still validby reference to the stored RRC connection data; and

in response to the RAN node determining that the suspended RRCconnection is still valid, sending a reactivation request completemessage to the UE and thereafter resuming user plane data transfer withthe UE over the reactivated RRC connection; or

in response to the RAN node determining that the suspended RRCconnection is invalid, sending a reactivation request reject message tothe UE.

20. A method as set out in clause 19, wherein the RAN node determiningwhether or not the suspended RRC connection is still valid comprises atleast one of:

-   -   determining that a timer has not expired; and    -   determining that the RRC connection has not been released.

21. A method as set out in any preceding clause, wherein the UE isconfigured to communicate with the RAN in accordance with the LTE or LTEAdvanced protocols.

22. A method as set out in any preceding clause, wherein the RAN isconfigured to communicate with the UE in accordance with the LTE or LTEAdvanced protocols.

23. A method as set out in any preceding clause, wherein the RAN node ornodes is/are eNode B(s).

24. A node of a Radio Access Network (RAN) for use with a user equipment(UE), the RAN node being configured to:

suspend an established RRC connection with the UE;

thereafter be operable, whilst the RRC connection is suspended, to pagethe UE or transmit notification of downlink data for the UE or both; and

store RRC connection data related to the suspended RRC connection, saidRRC connection data being usable by the RAN node reactivate thesuspended RRC connection.

25. A RAN node as set out in clause 24, wherein RRC connection datacomprises data representing one or more of:

-   -   the configuration of radio bearers in the established RRC        connection;    -   security parameters relating to the established RRC connection;    -   temporary cell identifiers;    -   MAC configuration;    -   Physical Layer configuration.

26. A RAN node as set out in clause 24 or 25, further comprising markingthe stored RRC connection data to indicate the suspension of the RRCconnection.

27. A RAN node as set out in clause 24, 25 or 26, further comprising theRAN node being configured to suspend the established RRC connection inresponse to an RRC connection suspension criterion being met

28. A RAN node as set out in clause 27, wherein the RRC connectionsuspension criteria comprises one or more of:

-   -   the expiry of a timer at the RAN Node;    -   transmission of a message by the RAN node to the UE to instruct        suspension of the established RRC connection.

29. A RAN node as set out in any of clauses 24-28, further comprisingthe RAN node being configure to, in response to receiving an RRCconnection reactivation request message from the UE:

determine whether or not the suspended RRC connection is still valid byreference to the stored RRC connection data;

in response to the RAN node determining that the suspended RRCconnection is still valid, send a reactivation request complete messageto the UE and thereafter resuming user plane data transfer with the UEover the reactivated RRC connection; and

in response to the RAN node determining that the suspended RRCconnection is invalid, send a reactivation request reject message to theUE.

30. A RAN node as set out in clause 29, the RAN node being configuredsuch that the RAN node determining whether or not the suspended RRCconnection is still valid comprises at least one of:

-   -   determining that a timer has not expired; and    -   determining that the RRC connection has not been released.

31. A RAN node as set out in clause 29 or 30, further comprising the RANresuming mobility control of the UE as a result of reactivation of thesuspended RRC connection or a normal RRC connection process to establisha new RRC connection with the UE.

32. A RAN node as set out in any of clauses 24-31, wherein the RAN nodeis configured to communicate with the UE in accordance with the LTE orLTE Advanced protocols.

33. A RAN node as set out in any preceding clause, wherein the RAN nodeis an eNode B.

34. A RAN node as set out in any of clauses 24-33, wherein the RAN nodehas an established user plane connection with a Core Network (CN) forthe UE, further comprising maintaining the established user planeconnection between the RAN node and the CN while the RRC Connection issuspended.

35. A RAN node as set out in clause 34, the RAN node being configuredsuch that, when the RAN node receives from the CN downlink data for theUE, the RAN node buffers the downlink data and pages the UE or transmitsa notification of downlink data for the UE.

36. A RAN node as set out in clause 35, the RAN node being configuredsuch that, in response to the RAN node receiving no response from the UEto the paging or to the notification of downlink data, the RAN nodesends to the CN a paging escalation message.

37. A RAN node as set out in any of clauses 24-33, further comprisingthe UE or the RAN node sending a message to inform any node in the CoreNetwork (CN) that the RRC connection is suspended.

38. A RAN node as set out in clause 37, wherein the RAN node has anestablished user plane connection with a CN for the UE, furthercomprising suspending the established user plane connection between theCN and the RAN for the UE.

39. A RAN node as set out in clause 38, wherein the message sent to theCN includes an identification of the UE, the RAN node or one or more CNnodes or both being configured to:

discontinue transmission and reception of user plane data for the UEover the established user plane connection between the CN and the RANnode; and

store CN-RAN connection data representing the established user planeconnection with the CN, said CN-RAN connection data being usable tolater resume transmission and reception of user plane data to the UE byresuming said user plane connection between the CN and the RAN node asthe result of an RRC connection reactivation process.

40. A wireless communication system comprising a RAN node as set out inclauses 38 or 39 and a CN, wherein the CN is configured such that whendownlink data for the UE is received at the CN, a node of the CN buffersthe downlink data and the CN initiates the paging of the UE by one ormore cells of the RAN.

41. A wireless communication system comprising a RAN node as set out inclauses 38 or 39 and a CN or a wireless communication system as set outin clause 40, further comprising the wireless communication system beingconfigured such that a node of the CN maintains a validity indicator forthe UE, said validity indicator being usable in checking the validity ofthe said RRC connection as part of the RRC connection reactivationprocess.

42. A wireless communication system as set out in clause 41, wherein thevalue of the validity indicator is dependent on one or more of: thelocation of the user; a timer.

43. A RAN including a RAN node as set out in any of clauses 24-39,further comprising:

the RAN being configured to relinquish to the UE, mobility control ofthe UE until the RAN resumes mobility control of the UE as the result ofan RRC connection reactivation process or a normal RRC connectionprocess to establish a new RRC connection with the UE.

44. A RAN as set out in clause 43, wherein when the UE selects a cell ofthe RAN in which the suspended RRC Connection represented by the storedRRC connection data is invalid, the RAN receives a message informing theRAN of this event.

45. A RAN as set out in clause 44, wherein the RAN is configured suchthat receipt by the RAN of the message sent by the UE causes the RAN toperform one or more of: release the invalid suspended RRC Connection;initiate a new RRC connection with the UE; release an established userplane connection for the UE between the CN and RAN.

46. A computer program product having instructions which when carriedout by a processor of a node of a Radio Access Network (RAN) for usewith a user equipment (UE) cause the RAN node to be configured tooperate in accordance with a method as set out in any of clauses 1-23.

Additional aspects of the present disclosure relating to the operationof a CN node to suspend an RRC connection will now be set out in thefollowing numbered clauses.

1. A method, implemented in a node of a Core Network (CN) for use with anode of a Radio Access Network (RAN), comprising, in response to the CNreceiving a message indicating that an RRC connection between the RANand a user equipment (UE) is suspended:

the CN node discontinuing transmission and reception of user plane datafor the UE over an established user plane CN-RAN connection between theCN and the RAN node; and

storing CN-RAN connection data representing the established user planeconnection with the CN, said CN-RAN connection data being usable tolater resume transmission and reception of user plane data to the UE byresuming said user plane connection between the CN and the RAN node asthe result of the RRC connection being reactivated.

2. A method as set out in clause 1, wherein when downlink data for theUE is received at the CN, the method further comprising buffering thedownlink data in a node of the CN and initiating the paging of the UE byone or more cells of the RAN.

3. A method as set out in clause 1 or 2, further comprising, in responseto receiving a CN-RAN connection reactivation message at a node of theCN, resuming user plane data transfer between the CN and the RAN.

4. A method as set out in any preceding clause, wherein the CN node ispart of an Evolved Packet Core (EPC) configured to communicate inaccordance with the LTE or LTE Advanced protocols.

5. A node of a Core Network (CN) for use with a Radio Access Network(RAN), the node of the CN being configured to, in response to the CNreceiving a message indicating that an RRC connection between the RANand a user equipment (UE) is suspended:

discontinue transmission and reception of user plane data for the UEover an established user plane CN-RAN connection between the CN and theRAN node; and

store CN-RAN connection data representing the established user planeconnection with the CN, said CN-RAN connection data being usable tolater resume transmission and reception of user plane data to the UE byresuming said user plane connection between the CN and the RAN node asthe result of the RRC connection being reactivated.

6. A CN node as set out in clause 5, the CN node being configured suchthat, when downlink data for the UE is received at the CN, the CN nodebuffers the downlink data and initiates the paging of the UE by one ormore cells of the RAN.

7. A CN node as set out in clause 5 or 6, further comprising the CNnode, in response to receiving a CN-RAN connection reactivation messageat a node of the CN, resuming user plane data transfer with the RAN.

8. A CN node as set out in clause 5, 6 or 7, wherein the CN node is partof an Evolved Packet Core (EPC) configured to communicate in accordancewith the LTE or LTE Advanced protocols.

9. A computer program product having instructions which when carried outby a processor of a node of a Core Network (CN) for use with a RadioAccess Network (RAN) cause the node of the CN to be configured tooperate in accordance with a method as set out in any of clauses 1-4.

Additional aspects of the present disclosure relating to the operationof a UE or a RAN node for assessing the validity of a suspended RRCconnection and reactivating a suspended RRC connection will now be setout in the following numbered clauses.

1. A method, implemented in a node of a Radio Access Network (RAN) foruse with a user equipment (UE), an established RRC connection betweenthe RAN node and a UE having been suspended and RRC connection datarelated to the suspended RRC connection having been stored by the RANnode, the method comprising:

receiving at the RAN node an RRC connection reactivation request messagefrom the UE;

determining whether or not the suspended RRC connection is still validby reference to the stored RRC connection data; and

in response to the RAN node determining that the suspended RRCconnection is still valid, the RAN node sending a reactivation requestcomplete message to the UE and thereafter resuming user plane datatransfer with the UE over the reactivated RRC connection; or

in response to the RAN node determining that the suspended RRCconnection is invalid, the RAN node sending a reactivation requestreject message to the RAN.

2. A method as set out in clause 1, wherein the RAN node determiningwhether or not the suspended RRC connection is still valid comprises atleast one of:

-   -   determining that a timer has not expired; and    -   determining that the RRC connection has not been released.

3. A method as set out in clause 1 or 2, further comprising the RANresuming mobility control of the UE from the UE as a result ofreactivation of the suspended RRC connection or a normal RRC connectionprocess to establish a new RRC connection with the UE.

4. A method as set out in any preceding clause, wherein the RAN node ornodes is/are configured to communicate with the UE in accordance withthe LTE or LTE Advanced protocols.

5. A method as set out in any preceding clause, wherein the RAN node ornodes is/are eNode B(s).

6. A node of a Radio Access Network (RAN) for use with a user equipment(UE), the RAN node being configured such that when an established RRCconnection between the RAN node and a UE has been suspended and RRCconnection data related to the suspended RRC connection has been storedby the RAN node, in response to receiving at the RAN node an RRCconnection reactivation request message from the UE:

the RAN node determines whether or not the suspended RRC connection isstill valid by reference to the stored RRC connection data;

in response to the RAN node determining that the suspended RRCconnection is still valid, the RAN node sends a reactivation requestcomplete message to the UE and thereafter resuming user plane datatransfer with the UE over the reactivated RRC connection; and

in response to the RAN node determining that the suspended RRCconnection is invalid, the RAN node sends a reactivation request rejectmessage to the RAN.

7. A RAN node as set out in clause 6, further comprising the RAN nodebeing configured to determine whether or not the suspended RRCconnection is still valid by at least one of the RAN node:

-   -   determining that a timer has not expired; and    -   determining that the RRC connection has not been released.

8. A RAN comprising a RAN node as set out in clause 5 or 6, the RANbeing configured to resume mobility control of the UE from the UE as aresult of reactivation of the suspended RRC connection or a normal RRCconnection process to establish a new RRC connection with the UE.

9. A RAN node as set out in any of clauses 5-8, the RAN node or nodesbeing configured to communicate with the UE in accordance with the LTEor LTE Advanced protocols.

10. A RAN node as set out in any of clauses 5-9, wherein the RAN node ornodes is/are eNode B(s).

11. A computer program product having instructions which when carriedout by a processor of a node of a Radio Access Network (RAN) for usewith a user equipment (UE) cause the RAN node to be configured tooperate in accordance with a method as set out in any of clauses 1-5.

12. A method, implemented in a user equipment (UE) for use with a RadioAccess Network (RAN), an established RRC connection between a node ofthe RAN and the UE having been suspended and RRC connection data relatedto the suspended RRC connection having been stored by the UE, the methodcomprising:

the UE determining whether or not the suspended RRC connection is stillvalid by reference to the stored RRC connection data; and

in response to the UE determining that the suspended RRC connection isstill valid, the UE: transmitting to the RAN node an RRC connectionreactivation request message; and, in response to receiving from the RANnode an RRC connection reactivation accept message, the UE thereafterresuming user plane data transfer with the RAN node over the reactivatedRRC connection, or in response to receiving from the RAN node an RRCconnection reactivation reject message, the UE releasing the RRCconnection; or

in response to the UE determining that the suspended RRC connection isinvalid, the UE releasing the RRC connection.

13. A method as set out in clause 12, wherein the UE determining whetheror not the suspended RRC connection is still valid comprises at leastone of:

-   -   determining whether the UE is currently in a cell of the RAN in        which the suspended RRC Connection represented by the stored RRC        connection data is still valid; and    -   determining whether a timer has not expired.

14. A method as set out in clause 12 or 13, further comprising, inresponse to receiving RRC connection reactivation reject message or theUE determining that the suspended RRC connection is invalid, the UE alsoentering idle mode and thereafter initiating a normal RRC connectionestablishment process to establish a new RRC connection with the RAN.

15. A method as set out in clause 12, 13 or 14, further comprising theUE relinquishing mobility control of the UE to the RAN as a result ofreactivation of the suspended RRC connection or a normal RRC connectionprocess to establish a new RRC connection with the RAN.

16. A method as set out in any of clauses 12-15, wherein the UE isconfigured to communicate with the RAN in accordance with the LTE or LTEAdvanced protocols.

17. A User Equipment (UE) for use with a Radio Access Network (RAN), theUE being configured such that when an established RRC connection betweena node of the RAN and the UE has been suspended and RRC connection datarepresenting configuration information and state information related tothe suspended RRC connection has been stored by the UE:

the UE determines whether or not the suspended RRC connection is stillvalid by reference to the stored RRC connection data;

in response to the UE determining that the suspended RRC connection isstill valid, the UE transmits to the RAN node an RRC connectionreactivation request message; and, in response to receiving from the RANnode an RRC connection reactivation accept message, the UE thereafterresumes user plane data transfer with the RAN node over the reactivatedRRC connection, or in response to receiving from the RAN node an RRCconnection reactivation reject message, the UE releases the RRCconnection; and

in response to the UE determining that the suspended RRC connection isinvalid, the UE releases the RRC connection.

18. A UE set out in clause 17, further comprising the UE beingconfigured to determine whether or not the suspended RRC connection isstill valid by at least one of the UE:

-   -   determining whether the UE is currently in a cell of the RAN in        which the suspended RRC Connection represented by the stored RRC        connection data is still valid; and    -   determining whether a timer has not expired.

19. A UE as set out in clause 17 or 18, further comprising the UE beingconfigured such that, in response to receiving RRC connectionreactivation reject message or the UE determining that the suspended RRCconnection is invalid, the UE also enters idle mode and thereafterinitiates a normal RRC connection establishment process to establish anew RRC connection with the RAN.

20. A UE as set out in clause 17, 18 or 19, further comprising the UEbeing configured to relinquish mobility control of the UE to the RAN asa result of the reactivation of the suspended RRC connection or a normalRRC connection process to establish a new RRC connection with the RAN.

21. A UE as set out in any of clauses 17-20, wherein the UE isconfigured to communicate with the RAN in accordance with the LTE or LTEAdvanced protocols.

22. A computer program product having instructions which when carriedout by a processor of User Equipment (UE) for use with a Radio AccessNetwork (RAN) connection cause the UE to be configured to operate inaccordance with a method as set out in any of clauses 12-16.

Additional aspects of the present disclosure relating to the operationof a CN node or a RAN node for handling downlink data while an RRCconnection is suspended will now be set out in the following numberedclauses.

1. A method, implemented in a node of a Radio Access Network (RAN) foruse with a user equipment (UE), an established RRC connection between aRAN node and a UE having been suspended and RRC connection data relatedto the suspended RRC connection having been stored by the RAN node, themethod comprising:

the RAN node receiving downlink data for the UE;

the RAN node buffering the downlink data; and

the RAN node paging the UE or transmitting notification of downlink datafor the UE.

2. A method as set out in clause 1, wherein, in response to the RAN nodereceiving no response from the UE to the paging or to the notificationof downlink data, the RAN node sends to the CN a paging escalationmessage.

3. A method as set out in clause 2, further comprising:

receiving at the RAN node an RRC connection reactivation request messagefrom the UE;

determining whether or not the suspended RRC connection is still validby reference to the stored RRC connection data; and

in response to the RAN node determining that the suspended RRCconnection is still valid, the RAN node sending a reactivation requestcomplete message to the UE and thereafter resuming user plane datatransfer with the UE over the reactivated RRC connection; or

in response to the RAN node determining that the suspended RRCconnection is invalid, the RAN node sending a reactivation requestreject message to the RAN.

4. A method as set out in any preceding clause, wherein the RAN node isconfigured to communicate with the UE in accordance with the LTE or LTEAdvanced protocols.

5. A method as set out in any preceding clause, wherein the RAN node isan eNode B.

6. A node of a Radio Access Network (RAN) for use with a user equipment(UE), the RAN node being configured such that when an established RRCconnection between the RAN node and a UE has been suspended and RRCconnection data related to the suspended RRC connection has been storedby the RAN node, in response to the RAN node receiving downlink data forthe UE:

the RAN node buffers the downlink data; and

the RAN node pages the UE or transmits a message giving notification ofdownlink data.

7. A RAN node as set out in clause 6, the RAN node being configured suchthat, in response to the RAN node receiving no response from the UE tothe paging message or to the message giving notification of downlinkdata, the RAN node sends to the CN a paging escalation message.

8. A RAN node as set out in clause 6, further comprising the RAN nodebeing configured such that, in response to the RAN node receiving an RRCconnection reactivation request message from the UE:

the RAN node determines whether or not the suspended RRC connection isstill valid by reference to the stored RRC connection data;

in response to the RAN node determining that the suspended RRCconnection is still valid, the RAN node sends a reactivation requestcomplete message to the UE and thereafter resuming user plane datatransfer with the UE over the reactivated RRC connection; and

in response to the RAN node determining that the suspended RRCconnection is invalid, the RAN node sends a reactivation request rejectmessage to the RAN.

9. A RAN node as set out in any of clauses 6-8, wherein the RAN node isconfigured to communicate with the UE in accordance with the LTE or LTEAdvanced protocols.

10. A method as set out in any of clauses 6-9, wherein the RAN node isan eNode B.

11. A computer program product having instructions which when carriedout by a processor of a node of a Radio Access Network (RAN) for usewith a user equipment (UE) cause the RAN node to be configured tooperate in accordance with a method as set out in any of clauses 1-5.

12. A method, implemented in a node of a Core Network (CN) for use witha node of a Radio Access Network (RAN), the transmission and receptionof user plane data for a user equipment (UE) over an established userplane CN-RAN connection for the UE between the CN and the RAN nodehaving been discontinued in response to the CN receiving a messageindicating that an RRC connection between the RAN and the UE issuspended and CN-RAN connection data representing the extant user planeconnection between the CN and the RAN having been stored, the methodcomprising:

receiving downlink data for the UE;

the CN node buffering the downlink data;

the CN node initiating the paging of the UE by one or more cells of theRAN.

13. A method as set out in clause 12, further comprising a node of theCN maintaining a validity indicator for the UE, said validity indicatorbeing usable in checking the validity of the said RRC connection as partof a RRC connection reactivation process.

14. A method as set out in clause 13, wherein the value of the validityindicator is dependent on one or more of: the location of the user; atimer.

15. A method as set out in any of clauses 12-14, wherein the CN node ispart of an Evolved Packet Core (EPC) configured to communicate inaccordance with the LTE or LTE Advanced protocols.

16. A node of a Core Network (CN) for use with a node of a Radio AccessNetwork (RAN), the CN node being configured such that when thetransmission and reception of user plane data for a user equipment (UE)over an established user plane CN-RAN connection for the UE between theCN and the RAN node has been discontinued in response to the CNreceiving a message indicating that an RRC connection between the RANand the UE is suspended and CN-RAN connection data representing theextant user plane connection between the CN and the RAN has been stored,in response to receiving downlink data for the UE:

the CN node buffers the downlink data;

the CN node initiates the paging of the UE by one or more cells of theRAN.

17. A CN node as set out in clause 16, further comprising a node of theCN maintaining a validity indicator for the UE, said validity indicatorbeing usable in checking the validity of the said RRC connection as partof a RRC connection reactivation process.

18. A CN node as set out in clause 17, wherein the value of the validityindicator is dependent on one or more of: the location of the user; atimer.

19. A CN node as set out in any of clauses 16-18, wherein the CN node ispart of an Evolved Packet Core (EPC) configured to communicate inaccordance with the LTE or LTE Advanced protocols.

20. A computer program product having instructions which when carriedout by a processor of a node of a Core Network (CN) for communicatingwith a Radio Access Network (RAN) via a CN-RAN connection cause the nodeof the CN to be configured to operate in accordance with a method as setout in any of clauses 12-15.

Additional aspects of the present disclosure relating to the operationof a UE for handling mobility of the UE while an RRC connection issuspended will now be set out in the following numbered clauses.

1. A method, implemented in a user equipment (UE) for use with a RadioAccess Network (RAN), an established RRC connection between a node ofthe RAN and the UE having been suspended and RRC connection data relatedto the suspended RRC connection having been stored by the UE, the methodcomprising:

the UE performing autonomous mobility control by cell selection orreselection processes during the time that the RRC connection issuspended and the UE relinquishing mobility control of the UE to the RANas a result of reactivation of the suspended RRC connection or a normalRRC connection process to establish a new RRC connection with the UE.

2. A method as set out in clause 1, wherein when the UE selects a cellof the RAN in which the suspended RRC connection represented by the RRCconnection data is invalid, the UE continues to store the RRC connectiondata and omits to perform any communication with the CN to inform the CNof the mobility of the UE.

3. A method as set out in clause 1, wherein when the UE selects a cellof the RAN in which the suspended RRC connection represented by thestored RRC connection data is invalid, the UE transmits a messageinforming the RAN or a core network (CN) of this event.

4. A method as set out in clause 3, wherein the UE also releases thesuspended RRC connection and enters idle mode as the result of selectinga cell of the RAN in which the RRC connection represented by the storedRRC connection data is invalid.

5. A method as set out in any preceding clause, wherein the UE isconfigured to communicate with the RAN in accordance with the LTE or LTEAdvanced protocols.

6. A User Equipment (UE) for communicating with a Radio Access Network(RAN), the UE being configured such that when an established RRCconnection between a node of the RAN and the UE has been suspended andRRC connection data related to the suspended RRC connection has beenstored by the UE:

the UE performs autonomous mobility control by cell selection orreselection processes during the time that the RRC connection issuspended; and

the UE relinquishes mobility control of the UE to the RAN as a result ofthe reactivation of the suspended RRC connection or a normal RRCconnection process to establish a new RRC connection with the UE.

7. A UE as set out in clause 6, further comprising the UE beingconfigured such that, when the UE selects a cell of the RAN in which thesuspended RRC connection represented by the RRC connection data isinvalid, the UE continues to store the RRC connection data and omits toperform any communication with the CN to inform the CN of the mobilityof the UE.

8. A UE as set out in clause 6, further comprising the UE beingconfigured such that, when the UE selects a cell of the RAN in which thesuspended RRC connection represented by the stored RRC connection datais invalid, the UE transmits a message informing the RAN or a corenetwork (CN) of this event.

9. A UE as set out in clause 8, further comprising the UE beingconfigured such that the UE also releases the suspended RRC connectionand enters idle mode as the result of selecting a cell of the RAN inwhich the RRC connection represented by the stored RRC connection datais invalid.

10. A UE as set out in any of clauses 6-9, wherein the UE is configuredto communicate with the RAN in accordance with the LTE or LTE Advancedprotocols.

11. A computer program product having instructions which when carriedout by a processor of User Equipment (UE) for use with a Radio AccessNetwork (RAN) connection cause the UE to be configured to operate inaccordance with a method as set out in any of clauses 1-5.

What is claimed is:
 1. A method, implemented in a node of a Radio AccessNetwork (RAN) for use with a mobile device, the method comprising:receiving at the RAN node a request from the mobile device forre-establishment of a radio resource control (RRC) connection suspendedby another RAN node; attempting, by the RAN node, to retrieve RRCconnection data relating to the suspended RRC connection; and if the RRCconnection is valid, sending a connection re-establishment commandmessage to the mobile device; and if the RRC connection is invalid,sending a connection re-establishment reject message to the mobiledevice.
 2. A method according to claim 1, wherein the RAN nodedetermines whether the suspended RRC connection is still valid byreference to the RRC connection data.
 3. A method as claimed in claim 2,wherein the RAN node determines whether or not the suspended RRCconnection is valid comprises at least one of determining that a timerhas not expired or whether the RRC connection data is retrieved.
 4. Amethod according to claim 1, wherein the RRC connection data isretrieved from another network component.
 5. A method according to claim4, wherein the other network component is a mobility management entity(MME).
 6. A method according to claim 4, wherein the other networkcomponent is the other RAN node.
 7. A method according to claim 1,wherein the RRC connection data has been stored in a memory device inthe RAN node by the other RAN node and the RAN node retrieves it fromthe memory device.
 8. A method according to claim 1, wherein the RANnode retrieves the stored RRC connection data and re-establishes thesuspended RRC connection in response to the mobile device responding toa paging request or a notification of downlink data.
 9. A methodaccording to claim 1, wherein the RAN node retrieves the stored RRCconnection data and re-establishes the suspended RRC connection inresponse to receiving a re-establishment request message from the mobiledevice for re-establishment of the suspended RRC connection.
 10. Amethod as claimed in claim 1, wherein the RAN node is configured tocommunicate with the mobile device in accordance with a Long TermEvolution (LTE) or a LTE Advanced protocol.
 11. A method as claimed inclaim 1, wherein the RAN node or nodes is/are eNode B(s).
 12. A node ofa Radio Access Network (RAN) for use with a mobile device, the RAN nodebeing configured to: receive a request for re-establishment of a radioresource control (RRC) connection suspended by another RAN node; attemptto retrieve RRC connection data relating to the suspended RRCconnection; if the RRC connection is valid, send a connectionre-establishment command message to the mobile device; and if the RRCconnection is invalid, send a connection re-establishment reject messageto the mobile device.
 13. A RAN node according to claim 12, furtherbeing configured to determine whether the suspended RRC connection isstill valid by reference to the retrieved RRC connection data.
 14. A RANnode as claimed in claim 13, wherein the RAN node determines whether ornot the suspended RRC connection is still valid by at least one ofdetermining that a timer has not expired or whether the RRC connectiondata is retrieved.
 15. A RAN node according to claim 12, further beingconfigured to retrieve the RRC connection data from another networkcomponent.
 16. A RAN node according to claim 15, wherein the othernetwork component is a mobility management entity (MME).
 17. A RAN nodeaccording to claim 15, wherein the other network component is the otherRAN node.
 18. A RAN node according to claim 12, wherein the RAN nodeincludes a memory device and the RRC connection data has been receivedfrom the other RAN node and stored in the memory device, and the RANnode retrieves it from the memory device.
 19. A RAN node as claimed inclaim 12, the RAN node or nodes being configured to communicate with themobile device in accordance with a LTE or a LTE Advanced protocol.
 20. ARAN node as claimed in claim 12, wherein the RAN node is an eNode B. 21.A computer program product encoded on a tangible, non-transitory storagemedium, the product comprising computer readable instructions forcausing one or more processors to perform operations comprising:receiving, at a RAN node, a request from the mobile device forre-establishment of a radio resource control (RRC) connection suspendedby another RAN node; retrieving RRC connection data relating to thesuspended RRC connection; and if the RRC connection is valid, sending aconnection re-establishment command message to the mobile device; and ifthe RRC connection is invalid, sending a connection re-establishmentreject message to the mobile device.